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MEDIUM severity

CVE-2021-38186 — comrak

MEDIUMFix: kivikakk/comrak@b72340c

CVE-2021-38186 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in comrak. 1 public exploit reference exists, so weaponization risk is real. A fix is available for comrak — see the affected versions and patch details below.

Cross-site Scripting in comrak

Also known asGHSA-6wj2-g87r-pm62RUSTSEC-2021-0063
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 6, 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 CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk
0.00%0.41%0.83%1.24%0.2%0.7%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-38186 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🦀comrak

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 comrak crate before 0.10.1 for Rust. It mishandles & characters, leading to XSS via &# HTML entities.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iocomrakall versions0.10.1cargo update -p comrak --precise 0.10.1

Affected Products

1 product · 1 configurations
Application
comrakcomrak_project
< 0.10.1
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 comrak crate before 0.10.1 for Rust. It m…

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 comrak, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update comrak to 0.10.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-38186 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 comrak crate before 0.10.1 for Rust. It mishandles & characters, leading to XSS via &# HTML entities.
O3 Security · Impact-Aware SCA

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CVE-2021-38186: comrak XSS — Fixed in 0.10.1