Vulnerability-Lookup

CVE-2026-63430 (GCVE-0-2026-63430)

Vulnerability from cvelistv5 – Published: 2026-10-15 18:10 – Updated: 2026-10-15 20:25

Title

ammonia: mXSS in ammonia via MathML `annotation-xml` encoding strip

Summary

ammonia is a Rust library for repairing and securing untrusted HTML. Prior to 3.3.2, 4.0.2, and 4.1.3, applications that explicitly allow the math tag, annotation-xml, and at least one raw-text HTML element while disallowing the encoding attribute can permit mutation cross-site scripting. ammonia does not correctly implement annotation-xml's encoding-dependent MathML integration-point behavior after attribute filtering removes encoding, so the sanitizer validates a descendant under one namespace interpretation while the browser reparses the output under another. An attacker can use that namespace transition and an allowed raw-text HTML element to execute JavaScript when a user renders the sanitized output. The required tags are not enabled by default, so applications that do not explicitly allow them are not affected. This issue is fixed in versions 3.3.2, 4.0.2, and 4.1.3.

Severity

6.3 (Medium)


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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-15 20:24 UTC

CWE

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

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7752 records in the last 180 days details

References

12 references

URL	Tags
https://github.com/rust-ammonia/ammonia/security/…	x_refsource_CONFIRM
https://github.com/rust-ammonia/ammonia/pull/243	x_refsource_MISC
https://github.com/rust-ammonia/ammonia/pull/244	x_refsource_MISC
https://github.com/rust-ammonia/ammonia/pull/245	x_refsource_MISC
https://github.com/rust-ammonia/ammonia/commit/00…	x_refsource_MISC
https://github.com/rust-ammonia/ammonia/commit/7a…	x_refsource_MISC
https://github.com/rust-ammonia/ammonia/commit/b5…	x_refsource_MISC
https://github.com/rust-ammonia/ammonia/releases/…	x_refsource_MISC
https://github.com/rust-ammonia/ammonia/releases/…	x_refsource_MISC
https://github.com/rust-ammonia/ammonia/releases/…	x_refsource_MISC
https://ivan09999.github.io/ammonia-mxss	x_refsource_MISC
https://rustsec.org/advisories/RUSTSEC-2026-0193.html	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
rust-ammonia	ammonia	Affected: < 3.3.2 Affected: >= 4.0.0, < 4.0.2 Affected: >= 4.1.0, < 4.1.3	guessed

Show details on NVD website

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              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/rust-ammonia/ammonia/commit/004bf2cee4288f74a6ee619d589e3e90c24c09ca"
            },
            {
              "name": "https://github.com/rust-ammonia/ammonia/commit/7ac3fd3145236f28857eeecbadb544c8659cba31",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/rust-ammonia/ammonia/commit/7ac3fd3145236f28857eeecbadb544c8659cba31"
            },
            {
              "name": "https://github.com/rust-ammonia/ammonia/commit/b51bf4f9749ed3cd518330105f20a2c39c9ee274",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/rust-ammonia/ammonia/commit/b51bf4f9749ed3cd518330105f20a2c39c9ee274"
            },
            {
              "name": "https://github.com/rust-ammonia/ammonia/releases/tag/v3.3.2",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/rust-ammonia/ammonia/releases/tag/v3.3.2"
            },
            {
              "name": "https://github.com/rust-ammonia/ammonia/releases/tag/v4.0.2",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/rust-ammonia/ammonia/releases/tag/v4.0.2"
            },
            {
              "name": "https://github.com/rust-ammonia/ammonia/releases/tag/v4.1.3",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/rust-ammonia/ammonia/releases/tag/v4.1.3"
            },
            {
              "name": "https://ivan09999.github.io/ammonia-mxss",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://ivan09999.github.io/ammonia-mxss"
            },
            {
              "name": "https://rustsec.org/advisories/RUSTSEC-2026-0193.html",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://rustsec.org/advisories/RUSTSEC-2026-0193.html"
            }
          ],
          "source": {
            "advisory": "GHSA-9jh8-v38h-cvhr",
            "discovery": "UNKNOWN"
          },
          "title": "ammonia: mXSS in ammonia via MathML `annotation-xml` encoding strip"
        }
      },
      "cveMetadata": {
        "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "assignerShortName": "GitHub_M",
        "cveId": "CVE-2026-63430",
        "datePublished": "2026-10-15T18:10:35.869Z",
        "dateReserved": "2026-07-16T19:35:57.766Z",
        "dateUpdated": "2026-10-15T20:25:49.464Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

FKIE_CVE-2026-63430

Vulnerability from fkie_nvd - Published: 2026-10-15 19:17 - Updated: 2026-10-16 16:00

Severity

6.3 (Medium) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/commit/004bf2cee4288f74a6ee619d589e3e90c24c09ca
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/commit/7ac3fd3145236f28857eeecbadb544c8659cba31
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/commit/b51bf4f9749ed3cd518330105f20a2c39c9ee274
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/pull/243
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/pull/244
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/pull/245
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/releases/tag/v3.3.2
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/releases/tag/v4.0.2
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/releases/tag/v4.1.3
	security-advisories@github.com	https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr
	security-advisories@github.com	https://ivan09999.github.io/ammonia-mxss
	security-advisories@github.com	https://rustsec.org/advisories/RUSTSEC-2026-0193.html
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "ammonia",
          "vendor": "rust-ammonia",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 3.3.2"
            },
            {
              "status": "affected",
              "version": "\u003e= 4.0.0, \u003c 4.0.2"
            },
            {
              "status": "affected",
              "version": "\u003e= 4.1.0, \u003c 4.1.3"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "ammonia is a Rust library for repairing and securing untrusted HTML. Prior to 3.3.2, 4.0.2, and 4.1.3, applications that explicitly allow the math tag, annotation-xml, and at least one raw-text HTML element while disallowing the encoding attribute can permit mutation cross-site scripting. ammonia does not correctly implement annotation-xml\u0027s encoding-dependent MathML integration-point behavior after attribute filtering removes encoding, so the sanitizer validates a descendant under one namespace interpretation while the browser reparses the output under another. An attacker can use that namespace transition and an allowed raw-text HTML element to execute JavaScript when a user renders the sanitized output. The required tags are not enabled by default, so applications that do not explicitly allow them are not affected. This issue is fixed in versions 3.3.2, 4.0.2, and 4.1.3."
    }
  ],
  "id": "CVE-2026-63430",
  "lastModified": "2026-10-16T16:00:33.533",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.3,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "LOW",
          "subIntegrityImpact": "LOW",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/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",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-63430",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-15T20:24:18.831464Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-15T19:17:42.367",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/commit/004bf2cee4288f74a6ee619d589e3e90c24c09ca"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/commit/7ac3fd3145236f28857eeecbadb544c8659cba31"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/commit/b51bf4f9749ed3cd518330105f20a2c39c9ee274"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/pull/243"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/pull/244"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/pull/245"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/releases/tag/v3.3.2"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/releases/tag/v4.0.2"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/releases/tag/v4.1.3"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://ivan09999.github.io/ammonia-mxss"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0193.html"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

RUSTSEC-2026-0193 (GHSA-9JH8-V38H-CVHR)

Vulnerability from osv_rustsec – Published: 2026-06-30 12:00 – Updated: 2026-07-17 05:23 – Source website

Summary

mXSS in ammonia via MathML `annotation-xml` encoding strip

Details

If a certain set of MathML tags are enabled, an attacker can inject arbitrary JavaScript code into the user's browser.

The annotation-xml tag has slightly different behavior than the other "integration point" tags in MathML and SVG, but ammonia didn't handle it, so it didn't correctly strip the namespace-incompatible tags.

This vulnerability only has an effect when the math and annotation-xml tags are both enabled, but the encoding attribute is disabled, because it relies on the following sequence of steps:

User writes code like <math><annotation-xml encoding="text/html"><gadget></annotation-xml></math>.
Namespace filtering checks the DOM, and it passes. <gadget> is parsed as HTML.
Attribute filter strips it down to <math><annotation-xml><gadget></annotation-xml></math>. Because the encoding attribute is gone, <gadget> is now parsed as MathML.
The gadget is written in such a way that it exploits the parsing differences between HTML and MathML.

Additionally, the gadget can only be written using a tag that is parsed as raw text in HTML. These elements are:

title
textarea
xmp
iframe
noembed
noframes
plaintext
noscript
style
script

Applications that do not explicitly allow any of these tags should not be affected, since none are allowed by default.

Discovered by: Ivan Ivančić · Date: 2026-06-29 · Found via local differential analysis and source review of ammonia's sanitisation pipeline; no third-party systems were tested.

References

URL

Type

	https://crates.io/crates/ammonia	PACKAGE
	https://rustsec.org/advisories/RUSTSEC-2026-0193.html	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "categories": [
          "format-injection"
        ],
        "cvss": null,
        "informational": null
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "ammonia",
        "purl": "pkg:cargo/ammonia"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.0-0"
            },
            {
              "fixed": "3.3.2"
            },
            {
              "introduced": "4.0.0"
            },
            {
              "fixed": "4.0.2"
            },
            {
              "introduced": "4.1.0"
            },
            {
              "fixed": "4.1.3"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [
    "GHSA-9jh8-v38h-cvhr",
    "CVE-2026-63430"
  ],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "If a certain set of MathML tags are enabled, an attacker can inject arbitrary JavaScript code into the user\u0027s browser.\n\nThe `annotation-xml` tag has slightly different behavior than the other \"integration point\"\ntags in MathML and SVG, but ammonia didn\u0027t handle it, so it didn\u0027t correctly\nstrip the namespace-incompatible tags.\n\nThis vulnerability only has an effect when the `math` and `annotation-xml` tags\nare both enabled, but the `encoding` attribute is disabled, because it relies\non the following sequence of steps:\n\n1. User writes code like `\u003cmath\u003e\u003cannotation-xml encoding=\"text/html\"\u003e\u003cgadget\u003e\u003c/annotation-xml\u003e\u003c/math\u003e`.\n2. Namespace filtering checks the DOM, and it passes. `\u003cgadget\u003e` is parsed as HTML.\n3. Attribute filter strips it down to `\u003cmath\u003e\u003cannotation-xml\u003e\u003cgadget\u003e\u003c/annotation-xml\u003e\u003c/math\u003e`. Because the encoding attribute is gone, `\u003cgadget\u003e` is now parsed as MathML.\n4. The gadget is written in such a way that it exploits the parsing differences between HTML and MathML.\n\nAdditionally, the gadget can only be written using a tag that is parsed as raw text in HTML.\nThese [elements] are:\n\n* title\n* textarea\n* xmp\n* iframe\n* noembed\n* noframes\n* plaintext\n* noscript\n* style\n* script\n\nApplications that do not explicitly allow any of these tags should not be affected, since none are allowed by default.\n\n[elements]: https://github.com/servo/html5ever/blob/045a0378f2b0f8d4a350793899cf722a2a9b3d11/html5ever/src/tree_builder/rules.rs\n\n---\n\n**Discovered by:** [Ivan Ivan\u010di\u0107](https://ivan09999.github.io/ammonia-mxss) \u00b7 **Date:** 2026-06-29 \u00b7 Found via local differential analysis and source review of ammonia\u0027s sanitisation pipeline; no third-party systems were tested.",
  "id": "RUSTSEC-2026-0193",
  "modified": "2026-07-17T05:23:11Z",
  "published": "2026-06-30T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/ammonia"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0193.html"
    }
  ],
  "related": [],
  "severity": [],
  "summary": "mXSS in ammonia via MathML `annotation-xml` encoding strip"
}

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.

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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.

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Action not permitted

CVE-2026-63430 (GCVE-0-2026-63430)

FKIE_CVE-2026-63430

RUSTSEC-2026-0193 (GHSA-9JH8-V38H-CVHR)

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