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MEDIUM severity

CVE-2021-38193 — ammonia

MEDIUMFix: rust-ammonia/ammonia#142

CVE-2021-38193 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in ammonia. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for ammonia — see the affected versions and patch details below.

Cross-site Scripting in ammonia

Also known asGHSA-5325-xw5m-phm3RUSTSEC-2021-0074
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
1 known
Exploitation data as of Nov 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk
0.00%0.40%0.81%1.21%0.2%0.7%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected
🦀ammonia🦀ammonia

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.

Description

An issue was discovered in the ammonia crate before 3.1.0 for Rust. XSS can occur because the parsing differences for HTML, SVG, and MathML are mishandled, a similar issue to CVE-2020-26870.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.ioammonia≥ 3.0.0&&< 3.1.03.1.0cargo update -p ammonia --precise 3.1.0
🦀crates.ioammoniaall versions2.1.3cargo update -p ammonia --precise 2.1.3

Affected Products

1 product · 1 configurations
Application
ammoniaammonia_project
< 3.1.0
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

An issue was discovered in the ammonia crate before 3.1.0 for Rust. XSS …

rustsec.orgNVDAug 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ammonia, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update ammonia to 3.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-38193 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

An issue was discovered in the ammonia crate before 3.1.0 for Rust. XSS can occur because the parsing differences for HTML, SVG, and MathML are mishandled, a similar issue to CVE-2020-26870.
O3 Security · Impact-Aware SCA

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CVE-2021-38193: ammonia XSS — Fixed in 3.1.0