CVE-2026-63430
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…
Does this matter?
Lower severity and a low EPSS score (0.56%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 4.0
- 6.3 MEDIUMCVSS: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/M
- EPSS
- 0.56% probability · 46th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-79
- Source
- security-advisories@github.com
EPSS moved from 0.6% on 16 October 2026 to 0.6% on 26 October 2026.
References
- 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/pull/243
- https://github.com/rust-ammonia/ammonia/pull/244
- https://github.com/rust-ammonia/ammonia/pull/245
- https://github.com/rust-ammonia/ammonia/releases/tag/v3.3.2
- https://github.com/rust-ammonia/ammonia/releases/tag/v4.0.2
- https://github.com/rust-ammonia/ammonia/releases/tag/v4.1.3
- https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr
- https://ivan09999.github.io/ammonia-mxss
- https://rustsec.org/advisories/RUSTSEC-2026-0193.html
- https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.