Vulnerability-Lookup

GHSA-238P-PMPM-9MQ7

Vulnerability from github – Published: 2026-10-05 23:41 – Updated: 2026-10-05 23:41

Summary

KaTeX: Existing prototype pollution can bypass trust restrictions

Details

Impact

KaTeX can act as a read-side prototype pollution gadget in applications where Object.prototype has already been polluted, or where an attacker can influence the prototype of the renderer options object. (KaTeX does not enable said prototype pollution. This advisory applies when combining KaTeX with other vulnerable software that allows for prototype pollution.)

Affected versions may treat inherited properties from Object.prototype as renderer options, internal setting metadata, or namespace entries. In particular, an inherited trust value will be treated as though the application explicitly enabled trusted rendering, rather than using the documented default of false.

With attacker-controlled mathematical expressions, this can produce links capable of user-interaction cross-site scripting or load attacker-selected external resources. Exploitation requires the consuming application to insert KaTeX output into a web page without a separate sanitizer. (KaTeX does not execute scripts merely by rendering an expression.)

Other inherited settings can alter rendering behavior or resource limits. Inherited setting metadata can affect how defaults and supplied options are processed, while inherited namespace properties can be mistaken for defined macros or other internal values.

Patches

Upgrade to KaTeX v0.18.2 to remove this vulnerability.

Workarounds

Address any prototype-pollution vulnerability in the application or its dependencies.
delete Object.prototype.trust, delete Object.prototype.default, and delete Object.prototype.processor before calling KaTeX
Do not allow untrusted input to control the renderer options object or its prototype.
Sanitize KaTeX-generated HTML before inserting it into a document.

Details

KaTeX previously used ordinary JavaScript property access in the following contexts:

Renderer settings could be inherited from the prototype of the options object.
Internal default and processor setting metadata could be inherited from Object.prototype.
Namespace lookup could treat inherited properties as built-in definitions.
Namespace group restoration could preserve an inherited property as though it had been an explicitly defined value.

The fix adds own-property checks to each of these paths. Inherited properties are no longer accepted as renderer settings, setting metadata, namespace definitions, or values to be restored after a group ends.

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

2.1 (Low)


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

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "katex"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.11.0"
            },
            {
              "fixed": "0.18.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-103923"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-807"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-05T23:41:05Z",
    "nvd_published_at": "2026-10-01T18:17:13Z",
    "severity": "LOW"
  },
  "details": "### Impact\n\nKaTeX can act as a read-side prototype pollution gadget in applications where `Object.prototype` has already been polluted, or where an attacker can influence the prototype of the renderer options object. (KaTeX does not enable said prototype pollution. This advisory applies when combining KaTeX with other vulnerable software that allows for prototype pollution.)\n\nAffected versions may treat inherited properties from `Object.prototype` as renderer options, internal setting metadata, or namespace entries. In particular, an inherited `trust` value will be treated as though the application explicitly enabled trusted rendering, rather than using the documented default of `false`.\n\nWith attacker-controlled mathematical expressions, this can produce links capable of user-interaction cross-site scripting or load attacker-selected external resources. Exploitation requires the consuming application to insert KaTeX output into a web page without a separate sanitizer. (KaTeX does not execute scripts merely by rendering an expression.)\n\nOther inherited settings can alter rendering behavior or resource limits. Inherited setting metadata can affect how defaults and supplied options are processed, while inherited namespace properties can be mistaken for defined macros or other internal values.\n\n### Patches\n\nUpgrade to KaTeX v0.18.2 to remove this vulnerability.\n\n### Workarounds\n\n- Address any prototype-pollution vulnerability in the application or its dependencies.\n- `delete Object.prototype.trust`, `delete Object.prototype.default`, and `delete Object.prototype.processor` before calling KaTeX\n- Do not allow untrusted input to control the renderer options object or its prototype.\n- Sanitize KaTeX-generated HTML before inserting it into a document.\n\n### Details\n\nKaTeX previously used ordinary JavaScript property access in the following contexts:\n\n- Renderer settings could be inherited from the prototype of the options object.\n- Internal `default` and `processor` setting metadata could be inherited from `Object.prototype`.\n- Namespace lookup could treat inherited properties as built-in definitions.\n- Namespace group restoration could preserve an inherited property as though it had been an explicitly defined value.\n\nThe fix adds own-property checks to each of these paths. Inherited properties are no longer accepted as renderer settings, setting metadata, namespace definitions, or values to be restored after a group ends.\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n\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-238p-pmpm-9mq7",
  "modified": "2026-10-05T23:41:05Z",
  "published": "2026-10-05T23:41:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/KaTeX/KaTeX/security/advisories/GHSA-238p-pmpm-9mq7"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103923"
    },
    {
      "type": "WEB",
      "url": "https://github.com/KaTeX/KaTeX/pull/4260"
    },
    {
      "type": "WEB",
      "url": "https://github.com/KaTeX/KaTeX/commit/0adf7e77db6915d991803b29699f82b1ccf8d4f4"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/KaTeX/KaTeX"
    },
    {
      "type": "WEB",
      "url": "https://github.com/KaTeX/KaTeX/releases/tag/v0.18.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "KaTeX: Existing prototype pollution can bypass trust restrictions"
}

CVE-2026-103923 (GCVE-0-2026-103923)

Vulnerability from cvelistv5 – Published: 2026-10-01 17:37 – Updated: 2026-10-06 01:59

Title

KaTeX: Existing prototype pollution can bypass trust restrictions

Summary

KaTeX is a fast, easy-to-use JavaScript library for TeX math rendering on the web. From 0.11.0 until 0.18.2, KaTeX uses ordinary JavaScript property access for the renderer options object, the trust setting, default and processor setting metadata, and namespace lookup and group restoration, allowing inherited properties to be treated as explicitly supplied values. When Object.prototype is already polluted or an attacker controls the options object's prototype, attacker-controlled mathematical expressions can use an inherited trust value to enable trusted rendering and produce links capable of user-interaction cross-site scripting or loading attacker-selected external resources in a consuming application that inserts unsanitized KaTeX output into a page. KaTeX does not itself create the prototype pollution, and rendering an expression alone does not execute script. This issue is fixed in version 0.18.2.

Severity

2.1 (Low)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-06 01:59 UTC

CWE

CWE-807 - Reliance on Untrusted Inputs in a Security Decision

Assigner

GitHub_M mitre root Scorecard

References

4 references

URL	Tags
https://github.com/KaTeX/KaTeX/security/advisorie…	x_refsource_CONFIRM
https://github.com/KaTeX/KaTeX/pull/4260	x_refsource_MISC
https://github.com/KaTeX/KaTeX/commit/0adf7e77db6…	x_refsource_MISC
https://github.com/KaTeX/KaTeX/releases/tag/v0.18.2	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
KaTeX	KaTeX	Affected: >= 0.11.0, < 0.18.2

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-103923",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-06T01:59:19.477369Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-06T01:59:30.896Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "KaTeX",
          "vendor": "KaTeX",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 0.11.0, \u003c 0.18.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "KaTeX is a fast, easy-to-use JavaScript library for TeX math rendering on the web. From 0.11.0 until 0.18.2, KaTeX uses ordinary JavaScript property access for the renderer options object, the trust setting, default and processor setting metadata, and namespace lookup and group restoration, allowing inherited properties to be treated as explicitly supplied values. When Object.prototype is already polluted or an attacker controls the options object\u0027s prototype, attacker-controlled mathematical expressions can use an inherited trust value to enable trusted rendering and produce links capable of user-interaction cross-site scripting or loading attacker-selected external resources in a consuming application that inserts unsanitized KaTeX output into a page. KaTeX does not itself create the prototype pollution, and rendering an expression alone does not execute script. This issue is fixed in version 0.18.2."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 2.1,
            "baseSeverity": "LOW",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "ACTIVE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/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"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-807",
              "description": "CWE-807: Reliance on Untrusted Inputs in a Security Decision",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-01T17:37:47.953Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/KaTeX/KaTeX/security/advisories/GHSA-238p-pmpm-9mq7",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/KaTeX/KaTeX/security/advisories/GHSA-238p-pmpm-9mq7"
        },
        {
          "name": "https://github.com/KaTeX/KaTeX/pull/4260",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/KaTeX/KaTeX/pull/4260"
        },
        {
          "name": "https://github.com/KaTeX/KaTeX/commit/0adf7e77db6915d991803b29699f82b1ccf8d4f4",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/KaTeX/KaTeX/commit/0adf7e77db6915d991803b29699f82b1ccf8d4f4"
        },
        {
          "name": "https://github.com/KaTeX/KaTeX/releases/tag/v0.18.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/KaTeX/KaTeX/releases/tag/v0.18.2"
        }
      ],
      "source": {
        "advisory": "GHSA-238p-pmpm-9mq7",
        "discovery": "UNKNOWN"
      },
      "title": "KaTeX: Existing prototype pollution can bypass trust restrictions"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-103923",
    "datePublished": "2026-10-01T17:37:47.953Z",
    "dateReserved": "2026-10-01T14:20:19.154Z",
    "dateUpdated": "2026-10-06T01:59:30.896Z",
    "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.

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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-238P-PMPM-9MQ7

Impact

Patches

Workarounds

Details

For more information

CVE-2026-103923 (GCVE-0-2026-103923)

Tags

Sightings

Nomenclature

Related by attack behaviour