How severe is CVE-2021-38193?

CVE-2021-38193 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-38193?

CVE-2021-38193 affects the following packages: ammonia (crates.io), ammonia (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2021-38193?

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.

How do I detect CVE-2021-38193 in my crates.io dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ammonia. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2021-38193 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2021-38193?

O3 pinpoints whether CVE-2021-38193 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2021-38193 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-38193, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-38193?

CVE-2021-38193 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 48th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-38193?

CVE-2021-38193 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-38193 published, and has it been updated?

CVE-2021-38193 was published on August 8, 2021 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🦀 crates.io

CVE-2021-38193

MEDIUM

Cross-site Scripting in ammonia

Also known asGHSA-5325-xw5m-phm3RUSTSEC-2021-0074

Published

Aug 8, 2021

Updated

Apr 10, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

1 known

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk48th percentile+0.50%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

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

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`ammonia`	≥ 3.0.0&&< 3.1.0	3.1.0
🦀crates.io	`ammonia`	all versions	2.1.3

Exploits & PoCs

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

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ammonia. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-38193 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2021-38193. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

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

Is CVE-2021-38193 in your dependencies?

O3 detects CVE-2021-38193 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works