---
id: CVE-2026-63430
title: ammonia is a Rust library for repairing and securing untrusted HTML
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…
severity: medium
cvss: 6.3
cvssVector: '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'
cwe:
  - CWE-79
vendor: rust-ammonia
product: ammonia
affected:
  - ammonia < 3.3.2
  - 'ammonia >= 4.0.0, < 4.0.2'
  - 'ammonia >= 4.1.0, < 4.1.3'
patched:
  - ammonia 4.1.3
published: '2026-10-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T16:00:33.533'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63430'
references:
  - url: >-
      https://github.com/rust-ammonia/ammonia/commit/004bf2cee4288f74a6ee619d589e3e90c24c09ca
    label: security-advisories@github.com
  - url: >-
      https://github.com/rust-ammonia/ammonia/commit/7ac3fd3145236f28857eeecbadb544c8659cba31
    label: security-advisories@github.com
  - url: >-
      https://github.com/rust-ammonia/ammonia/commit/b51bf4f9749ed3cd518330105f20a2c39c9ee274
    label: security-advisories@github.com
  - url: 'https://github.com/rust-ammonia/ammonia/pull/243'
    label: security-advisories@github.com
  - url: 'https://github.com/rust-ammonia/ammonia/pull/244'
    label: security-advisories@github.com
  - url: 'https://github.com/rust-ammonia/ammonia/pull/245'
    label: security-advisories@github.com
  - url: 'https://github.com/rust-ammonia/ammonia/releases/tag/v3.3.2'
    label: security-advisories@github.com
  - url: 'https://github.com/rust-ammonia/ammonia/releases/tag/v4.0.2'
    label: security-advisories@github.com
  - url: 'https://github.com/rust-ammonia/ammonia/releases/tag/v4.1.3'
    label: security-advisories@github.com
  - url: >-
      https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr
    label: security-advisories@github.com
  - url: 'https://ivan09999.github.io/ammonia-mxss'
    label: security-advisories@github.com
  - url: 'https://rustsec.org/advisories/RUSTSEC-2026-0193.html'
    label: security-advisories@github.com
  - url: >-
      https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://crates.io/crates/ammonia'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63430'
  - url: 'https://github.com/advisories/GHSA-9jh8-v38h-cvhr'
  - url: 'https://github.com/rust-ammonia/ammonia'
tags:
  - nvd
  - cve.org
  - osv
  - rust
  - exploit-available
  - ghsa
epss: 0.00555
epssPercentile: 0.46108
aliases:
  - RUSTSEC-2026-0193
  - GHSA-9jh8-v38h-cvhr
ecosystem: rust
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-15T20:24:18.831464Z'
cvssSource: cna
ingestedAt: '2026-07-17T19:00:52.026Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-63430)

Affected packages:

- `ammonia >= 4.1.0, < 4.1.3`

Patched in:

- `ammonia 4.1.3`

Source: https://osv.dev/vulnerability/RUSTSEC-2026-0193