GHSA-52p9-v744-mwjj is a critical-severity (CVSS 9.8) vulnerability in kramdown. 1 public exploit reference exists, so weaponization risk is real. A fix is available for kramdown — see the affected versions and patch details below.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-52p9-v744-mwjj by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
kramdownReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Kramdown before 2.3.1 does not restrict Rouge formatters to the Rouge::Formatters namespace, and thus arbitrary classes can be instantiated.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | kramdown | ≥ 1.16.0&&< 2.3.1 | 2.3.1bundle update kramdown --conservative |
Affected Products
debian linuxdebianfedorafedoraprojectkramdownkramdown_projectResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for kramdown, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update kramdown to 2.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-52p9-v744-mwjj 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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Red Hat supported products are not affected by this flaw because they do not ship rubygem-kramdown.
Developers using rubygem-kramdown: Do not pass user or external input into custom Rouge formatter selection logic. All other users/system administrators: There is no known mitigation at this time.Source: Red Hat security advisory for GHSA-52p9-v744-mwjj (CC BY 4.0)
Frequently Asked Questions
Is GHSA-52p9-v744-mwjj in your dependencies?
Find it across RubyGems, including transitive dependencies.