{"id":"RUSTSEC-2026-0193","revision":"4f338c9c577749c790d16ec1cf146c77","records":[{"revision":"4f338c9c577749c790d16ec1cf146c77","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"RUSTSEC-2026-0193","aliases":["CVE-2026-63430","GHSA-9jh8-v38h-cvhr"],"title":"mXSS in ammonia via MathML `annotation-xml` encoding strip","description":"If a certain set of MathML tags are enabled, an attacker can inject arbitrary JavaScript code into the user's browser.\n\nThe `annotation-xml` tag has slightly different behavior than the other \"integration point\"\ntags in MathML and SVG, but ammonia didn't handle it, so it didn't 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 `<math><annotation-xml encoding=\"text/html\"><gadget></annotation-xml></math>`.\n2. Namespace filtering checks the DOM, and it passes. `<gadget>` is parsed as HTML.\n3. 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.\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 Ivančić](https://ivan09999.github.io/ammonia-mxss) · **Date:** 2026-06-29 · Found via local differential analysis and source review of ammonia's sanitisation pipeline; no third-party systems were tested.","state":0,"publishedAt":"2026-06-30T12:00:00+00:00","modifiedAt":"2026-07-17T05:41:42.316382+00:00","affected":[{"ecosystem":"crates.io","name":"ammonia","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0.0.0-0"},{"kind":"fixed","version":"3.3.2"},{"kind":"introduced","version":"4.0.0"},{"kind":"fixed","version":"4.0.2"},{"kind":"introduced","version":"4.1.0"},{"kind":"fixed","version":"4.1.3"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://crates.io/crates/ammonia","https://rustsec.org/advisories/RUSTSEC-2026-0193.html"],"sourceUrl":"https://osv.dev/vulnerability/RUSTSEC-2026-0193","license":"OSV · upstream source license applies","key":"osv:RUSTSEC-2026-0193","identifiers":["RUSTSEC-2026-0193","CVE-2026-63430","GHSA-9jh8-v38h-cvhr"]},"retained":false,"historicalAffected":[]}],"coverage":[]}