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Common Weakness Enumeration

CWE-674

Allowed-with-Review

Uncontrolled Recursion

Abstraction: Class · Status: Draft

API response cwe.mitre.org

The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.

751 vulnerabilities reference this CWE, most recent first.

GHSA-62QF-JCQ8-8GXW

Vulnerability from github – Published: 2024-04-30 15:30 – Updated: 2024-05-01 11:08
VLAI
Summary
Duplicate Advisory: sqlparse parsing heavily nested list leads to Denial of Service
Details

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-2m57-hf25-phgg. This link is maintained to preserve external references.

Original Description

Passing a heavily nested list to sqlparse.parse() leads to a Denial of Service due to RecursionError.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "sqlparse"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.5.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-05-01T11:08:47Z",
    "nvd_published_at": "2024-04-30T15:15:53Z",
    "severity": "HIGH"
  },
  "details": "## Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-2m57-hf25-phgg. This link is maintained to preserve external references.\n\n## Original Description\nPassing a heavily nested list to sqlparse.parse() leads to a Denial of Service due to RecursionError.",
  "id": "GHSA-62qf-jcq8-8gxw",
  "modified": "2024-05-01T11:08:47Z",
  "published": "2024-04-30T15:30:38Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-4340"
    },
    {
      "type": "WEB",
      "url": "https://github.com/andialbrecht/sqlparse/commit/b4a39d9850969b4e1d6940d32094ee0b42a2cf03"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-2m57-hf25-phgg"
    },
    {
      "type": "WEB",
      "url": "https://research.jfrog.com/vulnerabilities/sqlparse-stack-exhaustion-dos-jfsa-2024-001031292"
    }
  ],
  "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": "Duplicate Advisory: sqlparse parsing heavily nested list leads to Denial of Service",
  "withdrawn": "2024-05-01T11:08:47Z"
}

GHSA-64FM-8HW2-V72W

Vulnerability from github – Published: 2024-03-25 19:38 – Updated: 2026-02-05 15:26
VLAI
Summary
KaTeX's maxExpand bypassed by `\edef`
Details

Impact

KaTeX users who render untrusted mathematical expressions could encounter malicious input using \edef that causes a near-infinite loop, despite setting maxExpand to avoid such loops. This can be used as an availability attack, where e.g. a client rendering another user's KaTeX input will be unable to use the site due to memory overflow, tying up the main thread, or stack overflow.

Patches

Upgrade to KaTeX v0.16.10 to remove this vulnerability.

Workarounds

Forbid inputs containing the substring "\\edef" before passing them to KaTeX. (There is no easy workaround for the auto-render extension.)

Details

KaTeX supports an option named maxExpand which prevents infinitely recursive macros from consuming all available memory and/or triggering a stack overflow error. However, what counted as an "expansion" is a single macro expanding to any number of tokens. The expand-and-define TeX command \edef can be used to build up an exponential number of tokens using only a linear number of expansions according to this definition, e.g. by repeatedly doubling the previous definition. This has been corrected in KaTeX v0.16.10, where every expanded token in an \edef counts as an expansion.

For more information

If you have any questions or comments about this advisory: * Open an issue or security advisory in the KaTeX repository * Email us at katex-security@mit.edu

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
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "katex"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.12.0"
            },
            {
              "fixed": "0.16.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-28243"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-606",
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-03-25T19:38:18Z",
    "nvd_published_at": "2024-03-25T20:15:07Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\nKaTeX users who render untrusted mathematical expressions could encounter malicious input using `\\edef` that causes a near-infinite loop, despite setting `maxExpand` to avoid such loops. This can be used as an availability attack, where e.g. a client rendering another user\u0027s KaTeX input will be unable to use the site due to memory overflow, tying up the main thread, or stack overflow.\n\n### Patches\nUpgrade to KaTeX v0.16.10 to remove this vulnerability.\n\n### Workarounds\nForbid inputs containing the substring `\"\\\\edef\"` before passing them to KaTeX.\n(There is no easy workaround for the auto-render extension.)\n\n### Details\nKaTeX supports an option named `maxExpand` which prevents infinitely recursive macros from consuming all available memory and/or triggering a stack overflow error. However, what counted as an \"expansion\" is a single macro expanding to any number of tokens. The expand-and-define TeX command `\\edef` can be used to build up an exponential number of tokens using only a linear number of expansions according to this definition, e.g. by repeatedly doubling the previous definition. This has been corrected in KaTeX v0.16.10, where every expanded token in an `\\edef` counts as an expansion.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue or security advisory in the [KaTeX repository](https://github.com/KaTeX/KaTeX/)\n* Email us at [katex-security@mit.edu](mailto:katex-security@mit.edu)",
  "id": "GHSA-64fm-8hw2-v72w",
  "modified": "2026-02-05T15:26:49Z",
  "published": "2024-03-25T19:38:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/KaTeX/KaTeX/security/advisories/GHSA-64fm-8hw2-v72w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-28243"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/6777"
    },
    {
      "type": "WEB",
      "url": "https://github.com/KaTeX/KaTeX/commit/e88b4c357f978b1bca8edfe3297f0aa309bcbe34"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/KaTeX/KaTeX"
    }
  ],
  "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": "KaTeX\u0027s maxExpand bypassed by `\\edef`"
}

GHSA-67FV-9R7G-432H

Vulnerability from github – Published: 2024-06-13 18:31 – Updated: 2024-07-05 21:21
VLAI
Summary
Rhai stack overflow vulenrability
Details

A stack overflow vulnerability was found in version 1.18.0 of rhai. The flaw position is: (/ SRC/rhai/SRC/eval/STMT. Rs in rhai: : eval: : STMT: : _ $LT $impl $u20 $rhai.. engine.. Engine$GT$::eval_stmt::h3f1d68ce37fc6e96). Due to the stack overflow is a recursive call/SRC/rhai/SRC/eval/STMT. Rs file eval_stmt_block function.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "rhai"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "1.18.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-36760"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-120",
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-06-13T22:03:59Z",
    "nvd_published_at": "2024-06-13T18:15:10Z",
    "severity": "HIGH"
  },
  "details": "A stack overflow vulnerability was found in version 1.18.0 of rhai. The flaw position is: (/ SRC/rhai/SRC/eval/STMT. Rs in rhai: : eval: : STMT: : _ $LT $impl $u20 $rhai.. engine.. Engine$GT$::eval_stmt::h3f1d68ce37fc6e96). Due to the stack overflow is a recursive call/SRC/rhai/SRC/eval/STMT. Rs file eval_stmt_block function.",
  "id": "GHSA-67fv-9r7g-432h",
  "modified": "2024-07-05T21:21:55Z",
  "published": "2024-06-13T18:31:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-36760"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rhaiscript/rhai/commit/308d07a11d3bff0d230f685a6320292181e5a445"
    },
    {
      "type": "WEB",
      "url": "https://github.com/MageWeiG/VulnerabilityCollection/blob/main/CVE-2024-36760/info.md"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/rhaiscript/rhai"
    }
  ],
  "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"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Rhai stack overflow vulenrability"
}

GHSA-685M-2W69-288Q

Vulnerability from github – Published: 2026-05-12 15:01 – Updated: 2026-05-14 20:35
VLAI
Summary
protobuf.js: Denial of service through unbounded protobuf recursion
Details

Summary

protobufjs could recurse without a depth limit while decoding nested protobuf data. This affected both skipping unknown group fields and generated decoding of nested message fields.

A crafted protobuf binary payload could cause the JavaScript call stack to be exhausted during decoding.

Impact

An attacker who can provide protobuf binary data decoded by an application may be able to crash the process or otherwise cause decoding to fail with a stack overflow.

This affects applications that decode untrusted protobuf binary input with affected versions.

Preconditions

  • The application must decode protobuf binary data influenced by an attacker.
  • The crafted input must contain deeply nested protobuf structures, such as nested group tags or nested message fields.
  • The affected decoder path must process the crafted input.

Workarounds

Avoid decoding untrusted protobuf binary data with affected versions. If immediate upgrade is not possible, reject excessively nested messages at an outer protocol boundary where feasible, or isolate protobuf decoding in a process that can be safely restarted.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 7.5.5"
      },
      "package": {
        "ecosystem": "npm",
        "name": "protobufjs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.5.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 8.0.1"
      },
      "package": {
        "ecosystem": "npm",
        "name": "protobufjs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0"
            },
            {
              "fixed": "8.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44289"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-12T15:01:05Z",
    "nvd_published_at": "2026-05-13T16:16:55Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nprotobufjs could recurse without a depth limit while decoding nested protobuf data. This affected both skipping unknown group fields and generated decoding of nested message fields.\n\nA crafted protobuf binary payload could cause the JavaScript call stack to be exhausted during decoding.\n\n## Impact\n\nAn attacker who can provide protobuf binary data decoded by an application may be able to crash the process or otherwise cause decoding to fail with a stack overflow.\n\nThis affects applications that decode untrusted protobuf binary input with affected versions.\n\n## Preconditions\n\n- The application must decode protobuf binary data influenced by an attacker.\n- The crafted input must contain deeply nested protobuf structures, such as nested group tags or nested message fields.\n- The affected decoder path must process the crafted input.\n\n## Workarounds\n\nAvoid decoding untrusted protobuf binary data with affected versions. If immediate upgrade is not possible, reject excessively nested messages at an outer protocol boundary where feasible, or isolate protobuf decoding in a process that can be safely restarted.",
  "id": "GHSA-685m-2w69-288q",
  "modified": "2026-05-14T20:35:08Z",
  "published": "2026-05-12T15:01:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-685m-2w69-288q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44289"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/protobufjs/protobuf.js"
    },
    {
      "type": "WEB",
      "url": "https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v7.5.6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.0.2"
    }
  ],
  "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": "protobuf.js: Denial of service through unbounded protobuf recursion"
}

GHSA-686H-RPGM-XJJ6

Vulnerability from github – Published: 2022-05-13 01:42 – Updated: 2022-05-13 01:42
VLAI
Details

There is a stack consumption issue in LibSass 3.4.5 that is triggered in the function Sass::Eval::operator() in eval.cpp. It will lead to a remote denial of service attack.

Severity
7.5 (High)
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2017-12964"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2017-08-18T21:29:00Z",
    "severity": "HIGH"
  },
  "details": "There is a stack consumption issue in LibSass 3.4.5 that is triggered in the function Sass::Eval::operator() in eval.cpp. It will lead to a remote denial of service attack.",
  "id": "GHSA-686h-rpgm-xjj6",
  "modified": "2022-05-13T01:42:49Z",
  "published": "2022-05-13T01:42:49Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2017-12964"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1482397"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-6C7J-GH7X-RW3H

Vulnerability from github – Published: 2022-05-24 21:59 – Updated: 2022-05-24 21:59
VLAI
Details

In Wireshark 3.0.0 to 3.0.1, 2.6.0 to 2.6.8, and 2.4.0 to 2.4.14, the dissection engine could crash. This was addressed in epan/packet.c by restricting the number of layers and consequently limiting recursion.

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
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{
  "affected": [],
  "aliases": [
    "CVE-2019-12295"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674",
      "CWE-94"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2019-05-23T12:29:00Z",
    "severity": "HIGH"
  },
  "details": "In Wireshark 3.0.0 to 3.0.1, 2.6.0 to 2.6.8, and 2.4.0 to 2.4.14, the dissection engine could crash. This was addressed in epan/packet.c by restricting the number of layers and consequently limiting recursion.",
  "id": "GHSA-6c7j-gh7x-rw3h",
  "modified": "2022-05-24T21:59:59Z",
  "published": "2022-05-24T21:59:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-12295"
    },
    {
      "type": "WEB",
      "url": "https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=15778"
    },
    {
      "type": "WEB",
      "url": "https://code.wireshark.org/review/gitweb?p=wireshark.git;a=commit;h=7b6e197da4c497e229ed3ebf6952bae5c426a820"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2020/10/msg00036.html"
    },
    {
      "type": "WEB",
      "url": "https://support.f5.com/csp/article/K06725231"
    },
    {
      "type": "WEB",
      "url": "https://support.f5.com/csp/article/K06725231?utm_source=f5support\u0026amp;utm_medium=RSS"
    },
    {
      "type": "WEB",
      "url": "https://usn.ubuntu.com/4133-1"
    },
    {
      "type": "WEB",
      "url": "https://www.wireshark.org/security/wnpa-sec-2019-19.html"
    },
    {
      "type": "WEB",
      "url": "http://www.securityfocus.com/bid/108464"
    }
  ],
  "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"
    }
  ]
}

GHSA-6G73-98RG-CRM7

Vulnerability from github – Published: 2026-08-16 15:30 – Updated: 2026-08-16 15:30
VLAI
Details

Scriban before 7.0.0 (affected versions <= 6.6.0) contains a stack overflow vulnerability in nested array initializer parsing. Deeply nested array initializers recurse through a path (ParseArrayInitializer → ParseExpression → ParseArrayInitializer) that is not covered by the ExpressionDepthLimit counter added in the fix for GHSA-wgh7-7m3c-fx25. An attacker who can supply untrusted input to Template.Parse can trigger an uncatchable StackOverflowException that immediately terminates the process, even with the default ExpressionDepthLimit enabled.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2026-74792"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-16T14:16:57Z",
    "severity": "HIGH"
  },
  "details": "Scriban before 7.0.0 (affected versions \u003c= 6.6.0) contains a stack overflow vulnerability in nested array initializer parsing. Deeply nested array initializers recurse through a path (ParseArrayInitializer \u2192 ParseExpression \u2192 ParseArrayInitializer) that is not covered by the ExpressionDepthLimit counter added in the fix for GHSA-wgh7-7m3c-fx25. An attacker who can supply untrusted input to Template.Parse can trigger an uncatchable StackOverflowException that immediately terminates the process, even with the default ExpressionDepthLimit enabled.",
  "id": "GHSA-6g73-98rg-crm7",
  "modified": "2026-08-16T15:30:27Z",
  "published": "2026-08-16T15:30:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/scriban/scriban/security/advisories/GHSA-p6q4-fgr8-vx4p"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74792"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/scriban-before-stack-overflow-via-nested-array-initializers"
    }
  ],
  "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"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/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"
    }
  ]
}

GHSA-6M44-FPC8-C3RQ

Vulnerability from github – Published: 2026-09-02 15:14 – Updated: 2026-09-02 15:14
VLAI
Summary
Mistune: Denial of Service — RecursionError via Excessive Emphasis Markers in Markdown
Details

Summary

Mistune v3.3.2 is vulnerable to a Denial of Service (DoS) attack via uncontrolled recursion in the HTML rendering of deeply-nested emphasis tokens. By submitting Markdown containing approximately 1,000 consecutive asterisk characters, an attacker causes the Python process to crash with RecursionError.

Details

The InlineParser's _process_emphasis_delimiters() creates deeply nested tokens from consecutive emphasis markers (every 2 asterisks add one nesting level). With 1,000 consecutive asterisks, approximately 500 levels of nesting are produced. The HTMLRenderer.render_token() method (src/mistune/renderers/html.py:40-57) renders these tokens recursively: when a token has children, line 48 calls self.render_tokens(token['children'], state), entering child rendering. Each nesting level produces ~2 stack frames, so 500 levels ≈ 1,000 frames, exceeding Python's default recursion limit (sys.getrecursionlimit() = 1000). The emphasis() and strong() methods (lines 80-84) wrap recursively rendered child content in and tags, perpetuating the recursion. This vulnerability affects all mistune APIs including markdown() and html().

Core vulnerable code path:

# src/mistune/renderers/html.py:40-57
def render_token(self, token: Dict[str, Any], state: BlockState) -> str:
    func = self._get_method(token["type"])
    attrs = token.get("attrs")
    if "raw" in token:
        text = token["raw"]
    elif "children" in token:
        text = self.render_tokens(token["children"], state)
    else:
        if attrs:
            return func(**attrs)
        else:
            return func()
    if attrs:
        return func(text, **attrs)
    else:
        return func(text)

The recursive call to render_tokens() on line 48 processes nested child tokens. With 500 levels of nested emphasis/strong tokens, this recursion exceeds Python's default recursion limit of 1000, causing a RecursionError.

# src/mistune/renderers/html.py:80-84
def emphasis(self, text: str) -> str:
    return "<em>" + text + "</em>"

def strong(self, text: str) -> str:
    return "<strong>" + text + "</strong>"

The emphasis() and strong() methods wrap their text content (which is itself the recursively-rendered output of nested child tokens) in HTML tags, creating the chain of recursion: each call to strong() includes rendered children that themselves call strong(), etc.

POC

from mistune import html

payload = '*' * 1000
try:
    result = html(payload)
    print('No crash - recursion handled')
except RecursionError as e:
    print(f'[VULN] RecursionError: {e} - Process would crash!')
except Exception as e:
    print(f'Error: {type(e).__name__}: {e}')

1

Impact

CVSS 3.1: 7.5 (High) — AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. An attacker can crash any server process using mistune with approximately 2KB of Markdown input. In web applications, this can be triggered through user-generated content such as forum posts or comments, causing denial of service for all concurrent users sharing the same Python process. Both mistune.markdown() and mistune.html() are affected.

Remediation

  1. Add a maximum nesting depth limit in the emphasis parsing stage, similar to BlockParser's max_nested_level mechanism (currently at DEFAULT_MAX_NESTED_LEVEL = 20). When the limit is exceeded, treat excess emphasis markers as literal text. 2. Alternatively, refactor HTMLRenderer to use an explicit stack-based iterative approach instead of recursive calls for rendering nested tokens. 3. As a defense-in-depth measure, document the recursion risk and recommend that applications deploying mistune set a higher recursion limit or implement request-level timeouts.
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": "PyPI",
        "name": "mistune"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.3.0"
            },
            {
              "fixed": "3.3.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-76098"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-02T15:14:55Z",
    "nvd_published_at": "2026-08-24T20:17:19Z",
    "severity": "HIGH"
  },
  "details": "## Summary\nMistune v3.3.2 is vulnerable to a Denial of Service (DoS) attack via uncontrolled recursion in the HTML rendering of deeply-nested emphasis tokens. By submitting Markdown containing approximately 1,000 consecutive asterisk characters, an attacker causes the Python process to crash with RecursionError.\n\n## Details\nThe InlineParser\u0027s _process_emphasis_delimiters() creates deeply nested \u003cstrong\u003e tokens from consecutive emphasis markers (every 2 asterisks add one nesting level). With 1,000 consecutive asterisks, approximately 500 levels of nesting are produced. The HTMLRenderer.render_token() method (src/mistune/renderers/html.py:40-57) renders these tokens recursively: when a token has children, line 48 calls self.render_tokens(token[\u0027children\u0027], state), entering child rendering. Each nesting level produces ~2 stack frames, so 500 levels \u2248 1,000 frames, exceeding Python\u0027s default recursion limit (sys.getrecursionlimit() = 1000). The emphasis() and strong() methods (lines 80-84) wrap recursively rendered child content in \u003cem\u003e and \u003cstrong\u003e tags, perpetuating the recursion. This vulnerability affects all mistune APIs including markdown() and html().\n\nCore vulnerable code path:\n\n```python\n# src/mistune/renderers/html.py:40-57\ndef render_token(self, token: Dict[str, Any], state: BlockState) -\u003e str:\n    func = self._get_method(token[\"type\"])\n    attrs = token.get(\"attrs\")\n    if \"raw\" in token:\n        text = token[\"raw\"]\n    elif \"children\" in token:\n        text = self.render_tokens(token[\"children\"], state)\n    else:\n        if attrs:\n            return func(**attrs)\n        else:\n            return func()\n    if attrs:\n        return func(text, **attrs)\n    else:\n        return func(text)\n```\n\nThe recursive call to render_tokens() on line 48 processes nested child tokens. With 500 levels of nested emphasis/strong tokens, this recursion exceeds Python\u0027s default recursion limit of 1000, causing a RecursionError.\n\n```python\n# src/mistune/renderers/html.py:80-84\ndef emphasis(self, text: str) -\u003e str:\n    return \"\u003cem\u003e\" + text + \"\u003c/em\u003e\"\n\ndef strong(self, text: str) -\u003e str:\n    return \"\u003cstrong\u003e\" + text + \"\u003c/strong\u003e\"\n```\n\nThe emphasis() and strong() methods wrap their text content (which is itself the recursively-rendered output of nested child tokens) in HTML tags, creating the chain of recursion: each call to strong() includes rendered children that themselves call strong(), etc.\n\n## POC\n\n``` wiki\nfrom mistune import html\n\npayload = \u0027*\u0027 * 1000\ntry:\n    result = html(payload)\n    print(\u0027No crash - recursion handled\u0027)\nexcept RecursionError as e:\n    print(f\u0027[VULN] RecursionError: {e} - Process would crash!\u0027)\nexcept Exception as e:\n    print(f\u0027Error: {type(e).__name__}: {e}\u0027)\n```\n\n\u003cimg width=\"1139\" height=\"664\" alt=\"1\" src=\"https://github.com/user-attachments/assets/d2095b9f-0a6a-4bef-8013-cbc6946cf8f1\" /\u003e\n\n\n\n## Impact\nCVSS 3.1: 7.5 (High) \u2014 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. An attacker can crash any server process using mistune with approximately 2KB of Markdown input. In web applications, this can be triggered through user-generated content such as forum posts or comments, causing denial of service for all concurrent users sharing the same Python process. Both mistune.markdown() and mistune.html() are affected.\n\n## Remediation\n1. Add a maximum nesting depth limit in the emphasis parsing stage, similar to BlockParser\u0027s max_nested_level mechanism (currently at DEFAULT_MAX_NESTED_LEVEL = 20). When the limit is exceeded, treat excess emphasis markers as literal text. 2. Alternatively, refactor HTMLRenderer to use an explicit stack-based iterative approach instead of recursive calls for rendering nested tokens. 3. As a defense-in-depth measure, document the recursion risk and recommend that applications deploying mistune set a higher recursion limit or implement request-level timeouts.",
  "id": "GHSA-6m44-fpc8-c3rq",
  "modified": "2026-09-02T15:14:55Z",
  "published": "2026-09-02T15:14:55Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-6m44-fpc8-c3rq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-76098"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/0938fb781d0aded99de801b340ec1f8debeae5b2"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.3"
    }
  ],
  "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": "Mistune: Denial of Service \u2014 RecursionError via Excessive Emphasis Markers in Markdown"
}

GHSA-6MWQ-4J3F-RR3X

Vulnerability from github – Published: 2022-08-11 00:00 – Updated: 2026-03-06 21:30
VLAI
Details

Uncontrolled recursion in the Parse functions in go/parser before Go 1.17.12 and Go 1.18.4 allow an attacker to cause a panic due to stack exhaustion via deeply nested types or declarations.

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

{
  "affected": [],
  "aliases": [
    "CVE-2022-1962"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2022-08-10T20:15:00Z",
    "severity": "MODERATE"
  },
  "details": "Uncontrolled recursion in the Parse functions in go/parser before Go 1.17.12 and Go 1.18.4 allow an attacker to cause a panic due to stack exhaustion via deeply nested types or declarations.",
  "id": "GHSA-6mwq-4j3f-rr3x",
  "modified": "2026-03-06T21:30:30Z",
  "published": "2022-08-11T00:00:16Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-1962"
    },
    {
      "type": "WEB",
      "url": "https://go.dev/cl/417063"
    },
    {
      "type": "WEB",
      "url": "https://go.dev/issue/53616"
    },
    {
      "type": "WEB",
      "url": "https://go.googlesource.com/go/+/695be961d57508da5a82217f7415200a11845879"
    },
    {
      "type": "WEB",
      "url": "https://groups.google.com/g/golang-announce/c/nqrv9fbR0zE"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RQXU752ALW53OJAF5MG3WMR5CCZVLWW6"
    },
    {
      "type": "WEB",
      "url": "https://pkg.go.dev/vuln/GO-2022-0515"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-6P2W-7Q97-F8HF

Vulnerability from github – Published: 2022-05-24 16:51 – Updated: 2024-04-04 01:22
VLAI
Details

serde serde_yaml 0.6.0 to 0.8.3 is affected by: Uncontrolled Recursion. The impact is: Denial of service by aborting. The component is: from_* functions (all deserialization functions). The attack vector is: Parsing a malicious YAML file. The fixed version is: 0.8.4 and later.

Severity
6.5 (Medium)
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2019-1010183"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2019-07-25T13:15:00Z",
    "severity": "MODERATE"
  },
  "details": "serde serde_yaml 0.6.0 to 0.8.3 is affected by: Uncontrolled Recursion. The impact is: Denial of service by aborting. The component is: from_* functions (all deserialization functions). The attack vector is: Parsing a malicious YAML file. The fixed version is: 0.8.4 and later.",
  "id": "GHSA-6p2w-7q97-f8hf",
  "modified": "2024-04-04T01:22:07Z",
  "published": "2022-05-24T16:51:22Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-1010183"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dtolnay/serde-yaml/pull/105"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}
Mitigation
Implementation

Ensure that an end condition will be reached under all logic conditions. The end condition may include checking against the depth of recursion and exiting with an error if the recursion goes too deep. The complexity of the end condition contributes to the effectiveness of this action.

Mitigation
Implementation

Increase the stack size.

CAPEC-230: Serialized Data with Nested Payloads

Applications often need to transform data in and out of a data format (e.g., XML and YAML) by using a parser. It may be possible for an adversary to inject data that may have an adverse effect on the parser when it is being processed. Many data format languages allow the definition of macro-like structures that can be used to simplify the creation of complex structures. By nesting these structures, causing the data to be repeatedly substituted, an adversary can cause the parser to consume more resources while processing, causing excessive memory consumption and CPU utilization.

CAPEC-231: Oversized Serialized Data Payloads

An adversary injects oversized serialized data payloads into a parser during data processing to produce adverse effects upon the parser such as exhausting system resources and arbitrary code execution.

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