Vulnerability MediumRUSTSEC-2021-0074 · ammonia
RUSTSEC-2021-0074: Incorrect handling of embedded SVG and MathML leads to mutation XSS
Short answerA security vulnerability in the ammonia crate: Incorrect handling of embedded SVG and MathML leads to mutation XSS. GitHub rates it Medium. Fixed in 2.1.3, 3.1.0: update to a fixed version.
| Crate | ammonia |
|---|---|
| Type | Vulnerability (format-injection) |
| Affected versions | Before 2.1.3; from 3.0.0 before 3.1.0. |
| Fixed in | 2.1.3, 3.1.0 |
| Severity | Medium (GitHub rating) |
| Published | 2021-07-08 |
| Last changed | 2023-11-08 |
| Also known as | CVE-2021-38193, GHSA-5325-xw5m-phm3 |
What to do
- See which version you have:
cargo tree -i ammonia(it also shows which of your dependencies pulls it in). - Update within your version requirement:
cargo update -p ammonia. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for exampleammonia = "3.1.0") or update the dependency that pulls it in. - Check again with
cargo audit, or paste your Cargo.lock into our Cargo.toml checker.
Details from the advisory
Affected versions of this crate did not account for namespace-related parsing differences between HTML, SVG, and MathML. Even if the svg and math elements are not allowed, the underlying HTML parser still treats them differently. Running cleanup without accounting for these differing namespaces resulted in an "impossible" DOM, which appeared "safe" when examining the DOM tree, but when serialized and deserialized, could be exploited to inject arbitrary markup.
To exploit this, the application using this library must allow a tag that is parsed as raw text in HTML. These elements are:
- title
- textarea
- xmp
- iframe
- noembed
- noframes
- plaintext
- noscript
- style
- script
Applications that do not explicitly allow any of these tags should not be affected, since none are allowed by default.
References
- Package: crates.io/crates/ammonia
- Advisory: rustsec.org/advisories/RUSTSEC-2021-0074.html
- Web: github.com/rust-ammonia/ammonia/pull/142
From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.
Other advisories for ammonia
- Vulnerability HighRUSTSEC-2019-0001 · 2019-04-27Uncontrolled recursion leads to abort in HTML serialization
- VulnerabilityRUSTSEC-2021-0157 · 2021-10-10Incorrect escaping for `url("")` functions in CSS style attributes
- VulnerabilityRUSTSEC-2021-0158 · 2021-10-10XSS in ammonia via SVG `animateMotion`, `animateTransform`, and/or `animateColor` tags
- VulnerabilityRUSTSEC-2022-0003 · 2022-01-19Space bug in `clean_text`
- VulnerabilityRUSTSEC-2025-0071 · 2025-09-21Incorrect handling of embedded SVG and MathML leads to mutation XSS after removal
- VulnerabilityRUSTSEC-2026-0193 · 2026-06-30mXSS in ammonia via MathML `annotation-xml` encoding strip
- VulnerabilityRUSTSEC-2026-0213 · 2026-07-21XSS in ammonia via SVG `animate` and `set` animation tags
- VulnerabilityRUSTSEC-2026-0373 · 2026-10-16Missing case-insensitive matching for CSS url function
Up next
Same crateammonia: security historyEvery advisory for this crate, and whether it is safe to use today.Read it next →Did this answer your question?