Vulnerability-Lookup

GHSA-5RGX-MCQ5-R7WV

Vulnerability from github – Published: 2026-08-03 21:31 – Updated: 2026-08-03 21:31

Details

Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.

Oaskit.ErrorHandler.Default.format_reason/4 and Oaskit.ErrorHandler.Default.reason_to_html/1 in lib/oaskit/error_handler/default.ex render request-validation failures as an HTML page whenever the request's Accept header contains html, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or deepObject query parameter, which appear in the JSON Schema error's instance path when a schema rejects them (for example under additionalProperties: false), and the raw Content-Type header, reflected in unsupported-media-type errors when it fails to parse.

Because browsers send Accept: text/html on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom Content-Type, or attacker-controlled script on the victim's side is required. A payload such as filter[alert(document.domain)]=x terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin's cookies, session, and same-origin responses.

Both HTML error rendering and the vulnerable handler are enabled by default: Oaskit.Plugs.ValidateRequest defaults :html_errors to true and :error_handler to Oaskit.ErrorHandler.Default, so applications following the documented usage are affected without any opt-in.

This issue affects oaskit: from 0.1.0 before 0.14.1.

Severity

5.1 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

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{
  "affected": [],
  "aliases": [
    "CVE-2026-66296"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-03T20:17:25Z",
    "severity": "MODERATE"
  },
  "details": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\n\nOaskit.ErrorHandler.Default.format_reason/4 and Oaskit.ErrorHandler.Default.reason_to_html/1 in lib/oaskit/error_handler/default.ex render request-validation failures as an HTML page whenever the request\u0027s Accept header contains html, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or deepObject query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under additionalProperties: false), and the raw Content-Type header, reflected in unsupported-media-type errors when it fails to parse.\n\nBecause browsers send Accept: text/html on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom Content-Type, or attacker-controlled script on the victim\u0027s side is required. A payload such as filter[\u003c/code\u003e\u003c/h2\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e]=x terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\n\nBoth HTML error rendering and the vulnerable handler are enabled by default: Oaskit.Plugs.ValidateRequest defaults :html_errors to true and :error_handler to Oaskit.ErrorHandler.Default, so applications following the documented usage are affected without any opt-in.\n\nThis issue affects oaskit: from 0.1.0 before 0.14.1.",
  "id": "GHSA-5rgx-mcq5-r7wv",
  "modified": "2026-08-03T21:31:37Z",
  "published": "2026-08-03T21:31:37Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lud/oaskit/security/advisories/GHSA-h7xw-x8wr-xpcc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-66296"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lud/oaskit/commit/b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1"
    },
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-66296.html"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-66296"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-66296 (GCVE-0-2026-66296)

Vulnerability from cvelistv5 – Published: 2026-08-03 19:04 – Updated: 2026-08-03 19:50

Title

Reflected XSS in oaskit's default HTML error handler

Summary

Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler. Oaskit.ErrorHandler.Default.format_reason/4 and Oaskit.ErrorHandler.Default.reason_to_html/1 in lib/oaskit/error_handler/default.ex render request-validation failures as an HTML page whenever the request's Accept header contains html, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or deepObject query parameter, which appear in the JSON Schema error's instance path when a schema rejects them (for example under additionalProperties: false), and the raw Content-Type header, reflected in unsupported-media-type errors when it fails to parse. Because browsers send Accept: text/html on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom Content-Type, or attacker-controlled script on the victim's side is required. A payload such as filter[</code></h2><script>alert(document.domain)</script>]=x terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin's cookies, session, and same-origin responses. Both HTML error rendering and the vulnerable handler are enabled by default: Oaskit.Plugs.ValidateRequest defaults :html_errors to true and :error_handler to Oaskit.ErrorHandler.Default, so applications following the documented usage are affected without any opt-in. This issue affects oaskit: from 0.1.0 before 0.14.1.

Severity

5.1 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Assigner

EEF

References

4 references

URL	Tags
https://github.com/lud/oaskit/security/advisories…	vendor-advisoryrelated
https://cna.erlef.org/cves/CVE-2026-66296.html	related
https://osv.dev/vulnerability/EEF-CVE-2026-66296	related
https://github.com/lud/oaskit/commit/b70c6b2eaf0b…	patch

Impacted products

2 products

Vendor	Product	Version
lud	oaskit	Affected: 0.1.0 , < 0.14.1 (semver) cpe:2.3:a:lud:oaskit::::::elixir::*
lud	oaskit	Affected: 552de8ca0ff60617bea58bcafa451892d61a161c , < b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1 (git) cpe:2.3:a:lud:oaskit::::::elixir::*

Date Public

2026-07-05 00:00

Credits

Ludovic Dem Ludovic Dem Jonatan Männchen / EEF

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-66296",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-03T19:50:03.665445Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
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          }
        ],
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          "dateUpdated": "2026-08-03T19:50:27.860Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/lud/oaskit/security/advisories/GHSA-h7xw-x8wr-xpcc"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:lud:oaskit:*:*:*:*:*:elixir:*:*"
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          "modules": [
            "Elixir.Oaskit.ErrorHandler.Default"
          ],
          "packageName": "oaskit",
          "packageURL": "pkg:hex/oaskit",
          "product": "oaskit",
          "programFiles": [
            "lib/oaskit/error_handler/default.ex"
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            {
              "name": "\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:format_reason/4"
            },
            {
              "name": "\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:reason_to_html/1"
            }
          ],
          "repo": "https://github.com/lud/oaskit",
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          "cpes": [
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          "programFiles": [
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            }
          ],
          "repo": "https://github.com/lud/oaskit",
          "vendor": "lud",
          "versions": [
            {
              "lessThan": "b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1",
              "status": "affected",
              "version": "552de8ca0ff60617bea58bcafa451892d61a161c",
              "versionType": "git"
            }
          ]
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      "cpeApplicability": [
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              "cpeMatch": [
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          "type": "finder",
          "value": "Ludovic Dem"
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          "type": "remediation developer",
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      "datePublic": "2026-07-05T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eImproper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eOaskit.ErrorHandler.Default.format_reason/4\u003c/code\u003e and \u003ccode\u003eOaskit.ErrorHandler.Default.reason_to_html/1\u003c/code\u003e in \u003ccode\u003elib/oaskit/error_handler/default.ex\u003c/code\u003e render request-validation failures as an HTML page whenever the request\u0027s \u003ccode\u003eAccept\u003c/code\u003e header contains \u003ccode\u003ehtml\u003c/code\u003e, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or \u003ccode\u003edeepObject\u003c/code\u003e query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under \u003ccode\u003eadditionalProperties: false\u003c/code\u003e), and the raw \u003ccode\u003eContent-Type\u003c/code\u003e header, reflected in unsupported-media-type errors when it fails to parse.\u003c/p\u003e\n\u003cp\u003eBecause browsers send \u003ccode\u003eAccept: text/html\u003c/code\u003e on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom \u003ccode\u003eContent-Type\u003c/code\u003e, or attacker-controlled script on the victim\u0027s side is required. A payload such as \u003ccode\u003efilter[\u0026lt;/code\u0026gt;\u0026lt;/h2\u0026gt;\u0026lt;script\u0026gt;alert(document.domain)\u0026lt;/script\u0026gt;]=x\u003c/code\u003e terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\u003c/p\u003e\n\u003cp\u003eBoth HTML error rendering and the vulnerable handler are enabled by default: \u003ccode\u003eOaskit.Plugs.ValidateRequest\u003c/code\u003e defaults \u003ccode\u003e:html_errors\u003c/code\u003e to \u003ccode\u003etrue\u003c/code\u003e and \u003ccode\u003e:error_handler\u003c/code\u003e to \u003ccode\u003eOaskit.ErrorHandler.Default\u003c/code\u003e, so applications following the documented usage are affected without any opt-in.\u003c/p\u003e\n\u003cp\u003eThis issue affects oaskit: from 0.1.0 before 0.14.1.\u003c/p\u003e"
            },
            {
              "base64": false,
              "type": "text/markdown",
              "value": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\n\n`Oaskit.ErrorHandler.Default.format_reason/4` and `Oaskit.ErrorHandler.Default.reason_to_html/1` in `lib/oaskit/error_handler/default.ex` render request-validation failures as an HTML page whenever the request\u0027s `Accept` header contains `html`, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or `deepObject` query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under `additionalProperties: false`), and the raw `Content-Type` header, reflected in unsupported-media-type errors when it fails to parse.\n\nBecause browsers send `Accept: text/html` on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom `Content-Type`, or attacker-controlled script on the victim\u0027s side is required. A payload such as `filter[\u003c/code\u003e\u003c/h2\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e]=x` terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\n\nBoth HTML error rendering and the vulnerable handler are enabled by default: `Oaskit.Plugs.ValidateRequest` defaults `:html_errors` to `true` and `:error_handler` to `Oaskit.ErrorHandler.Default`, so applications following the documented usage are affected without any opt-in.\n\nThis issue affects oaskit: from 0.1.0 before 0.14.1."
            }
          ],
          "value": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\n\nOaskit.ErrorHandler.Default.format_reason/4 and Oaskit.ErrorHandler.Default.reason_to_html/1 in lib/oaskit/error_handler/default.ex render request-validation failures as an HTML page whenever the request\u0027s Accept header contains html, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or deepObject query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under additionalProperties: false), and the raw Content-Type header, reflected in unsupported-media-type errors when it fails to parse.\n\nBecause browsers send Accept: text/html on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom Content-Type, or attacker-controlled script on the victim\u0027s side is required. A payload such as filter[\u003c/code\u003e\u003c/h2\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e]=x terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\n\nBoth HTML error rendering and the vulnerable handler are enabled by default: Oaskit.Plugs.ValidateRequest defaults :html_errors to true and :error_handler to Oaskit.ErrorHandler.Default, so applications following the documented usage are affected without any opt-in.\n\nThis issue affects oaskit: from 0.1.0 before 0.14.1."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-591",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-591 Reflected XSS"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 5.1,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "ACTIVE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-79",
              "description": "CWE-79 Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-03T19:04:30.556Z",
        "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "shortName": "EEF"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory",
            "related"
          ],
          "url": "https://github.com/lud/oaskit/security/advisories/GHSA-h7xw-x8wr-xpcc"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://cna.erlef.org/cves/CVE-2026-66296.html"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://osv.dev/vulnerability/EEF-CVE-2026-66296"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/lud/oaskit/commit/b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1"
        }
      ],
      "source": {
        "discovery": "INTERNAL"
      },
      "title": "Reflected XSS in oaskit\u0027s default HTML error handler",
      "workarounds": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eDisable HTML error rendering so that validation failures are returned as JSON only:\u003c/p\u003e\n\u003cpre\u003e\u003ccode class=\"language-elixir\"\u003eplug Oaskit.Plugs.ValidateRequest, html_errors: false\n\u003c/code\u003e\u003c/pre\u003e\n\u003cp\u003eThis prevents the vulnerable HTML page from being rendered at all, on any oaskit version. Alternatively, configure a custom \u003ccode\u003e:error_handler\u003c/code\u003e that does not emit HTML built from request-derived values.\u003c/p\u003e"
            },
            {
              "base64": false,
              "type": "text/markdown",
              "value": "Disable HTML error rendering so that validation failures are returned as JSON only:\n\n```elixir\nplug Oaskit.Plugs.ValidateRequest, html_errors: false\n```\n\nThis prevents the vulnerable HTML page from being rendered at all, on any oaskit version. Alternatively, configure a custom `:error_handler` that does not emit HTML built from request-derived values."
            }
          ],
          "value": "Disable HTML error rendering so that validation failures are returned as JSON only:\n\nplug Oaskit.Plugs.ValidateRequest, html_errors: false\n\nThis prevents the vulnerable HTML page from being rendered at all, on any oaskit version. Alternatively, configure a custom :error_handler that does not emit HTML built from request-derived values."
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
    "assignerShortName": "EEF",
    "cveId": "CVE-2026-66296",
    "datePublished": "2026-08-03T19:04:30.556Z",
    "dateReserved": "2026-07-24T14:10:01.114Z",
    "dateUpdated": "2026-08-03T19:50:27.860Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

GHSA-5RGX-MCQ5-R7WV

CVE-2026-66296 (GCVE-0-2026-66296)

Tags

Sightings

Nomenclature