# CVE-2026-63430: rust-ammonia: ammonia is a Rust library for repairing and securing untrusted HTML

CVE-2026-63430 is fixed in 7 products on 1 platform, first by DEBIAN-CVE-2026-63430, released October 16, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-63430
- Priority: Routine
- CVSS: n/a (moderate)
- EPSS: 0.0056
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 15, 2026

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python-nh3 Fedora 43 | 0.2.21-10.fc43 | [FEDORA-2026-501E3B2ABF](https://patchblox.com/security/data/fix/linux/fedora-2026-501e3b2abf.md) | Nov 7, 2026 |
| Linux | python-nh3-debugsource Fedora 43 | 0.2.21-10.fc43 | [FEDORA-2026-501E3B2ABF](https://patchblox.com/security/data/fix/linux/fedora-2026-501e3b2abf.md) | Nov 7, 2026 |
| Linux | python3-nh3 Fedora 43 | 0.2.21-10.fc43 | [FEDORA-2026-501E3B2ABF](https://patchblox.com/security/data/fix/linux/fedora-2026-501e3b2abf.md) | Nov 7, 2026 |
| Linux | python3-nh3-debuginfo Fedora 43 | 0.2.21-10.fc43 | [FEDORA-2026-501E3B2ABF](https://patchblox.com/security/data/fix/linux/fedora-2026-501e3b2abf.md) | Nov 7, 2026 |
| Linux | rust-ammonia Debian 14 | 4.1.3-1 | [DEBIAN-CVE-2026-63430](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63430.md) | Oct 16, 2026 |
| Linux | rust-ammonia Fedora 43 | 4.1.8-1.fc43 | [FEDORA-2026-501E3B2ABF](https://patchblox.com/security/data/fix/linux/fedora-2026-501e3b2abf.md) | Nov 7, 2026 |
| Linux | rust-ammonia+default-devel Fedora 43 | 4.1.8-1.fc43 | [FEDORA-2026-501E3B2ABF](https://patchblox.com/security/data/fix/linux/fedora-2026-501e3b2abf.md) | Nov 7, 2026 |
| Linux | rust-ammonia-devel Fedora 43 | 4.1.8-1.fc43 | [FEDORA-2026-501E3B2ABF](https://patchblox.com/security/data/fix/linux/fedora-2026-501e3b2abf.md) | Nov 7, 2026 |

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Data as of 2026-11-09T19:38:12Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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