CVE-2026-63430 · GHSA-9jh8-v38h-cvhr
ammonia: mXSS via MathML `annotation-xml` encoding strip
- Risk score
- 47/100
- CVSS
- 6.3 v4.0
- Exploit chance (30 days)
- 0.6%
- Published
- 15 Oct 2026
Open in the live forecast Today's forecast
What to know
- What it is
- 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 im…
- Affected
- ammonia (rust) < 3.3.2; ammonia (rust) >= 4.0.0, < 4.0.2; ammonia (rust) >= 4.1.0, < 4.1.3
- Fix
- Upgrade ammonia to 3.3.2 or 4.0.2 or 4.1.3 (whichever matches your release line) or later.
- Exploitation
- No known exploitation
Why it is Yellow
- CVSS 6.3 medium
Affected packages
| Package | Ecosystem | Vulnerable | Fixed in |
|---|---|---|---|
| ammonia | rust | < 3.3.2 | 3.3.2 |
| ammonia | rust | >= 4.0.0, < 4.0.2 | 4.0.2 |
| ammonia | rust | >= 4.1.0, < 4.1.3 | 4.1.3 |
References
- https://github.com/advisories/GHSA-9jh8-v38h-cvhr
- https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr
- https://nvd.nist.gov/vuln/detail/CVE-2026-63430
- https://github.com/rust-ammonia/ammonia/pull/243
- https://github.com/rust-ammonia/ammonia/pull/244
- https://github.com/rust-ammonia/ammonia/pull/245
- https://github.com/rust-ammonia/ammonia/commit/004bf2cee4288f74a6ee619d589e3e90c24c09ca
- https://github.com/rust-ammonia/ammonia/commit/7ac3fd3145236f28857eeecbadb544c8659cba31
- https://github.com/rust-ammonia/ammonia/commit/b51bf4f9749ed3cd518330105f20a2c39c9ee274
- https://github.com/rust-ammonia/ammonia/releases/tag/v3.3.2
Original 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.
Last activity 15 Oct 2026. Patch Forecast updates every hour.