GHSA-fh2r-99q2-6mmg is a high-severity (CVSS 7.5) vulnerability in rustls-webpki. A fix is available for rustls-webpki — see the affected versions and patch details below.
rustls-webpki: CPU denial of service in certificate path building
Real-World Exposure
rustls-webpki🦀rustls-webpkiReal-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
When this crate is given a pathological certificate chain to validate, it will spend CPU time exponential with the number of candidate certificates at each step of path building.
Both TLS clients and TLS servers that accept client certificate are affected.
We now give each path building operation a budget of 100 signature verifications.
The original webpki crate is also affected, see GHSA-8qv2-5vq6-g2g7.
This was previously reported in the original crate https://github.com/briansmith/webpki/issues/69 and re-reported to us recently.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | rustls-webpki | all versions | 0.100.2cargo update -p rustls-webpki --precise 0.100.2 |
| 🦀crates.io | rustls-webpki | ≥ 0.101.0&&< 0.101.4 | 0.101.4cargo update -p rustls-webpki --precise 0.101.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rustls-webpki, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rustls-webpki to 0.100.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fh2r-99q2-6mmg 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-fh2r-99q2-6mmg can be triaged on real exposure rather than presence alone.
Tailored to GHSA-fh2r-99q2-6mmg. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-fh2r-99q2-6mmg in your dependencies?
O3 Security finds GHSA-fh2r-99q2-6mmg across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.