GHSA-FH2R-99Q2-6MMG

rustls-webpki: CPU denial of service in certificate path building

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.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

GHSA-FH2R-99Q2-6MMG has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.100.2, 0.101.4); upgrading removes the vulnerable code path.

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1. What is GHSA-FH2R-99Q2-6MMG? GHSA-FH2R-99Q2-6MMG is a high-severity uncontrolled resource consumption vulnerability in rustls-webpki (rust), affecting versions < 0.100.2. It is fixed in 0.100.2, 0.101.4. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is GHSA-FH2R-99Q2-6MMG? GHSA-FH2R-99Q2-6MMG has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of rustls-webpki are affected by GHSA-FH2R-99Q2-6MMG? rustls-webpki (rust) versions < 0.100.2 is affected.
4. Is there a fix for GHSA-FH2R-99Q2-6MMG? Yes. GHSA-FH2R-99Q2-6MMG is fixed in 0.100.2, 0.101.4. Upgrade to this version or later.
5. Is GHSA-FH2R-99Q2-6MMG exploitable, and should I be worried? Whether GHSA-FH2R-99Q2-6MMG is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-FH2R-99Q2-6MMG is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-FH2R-99Q2-6MMG?
   • Upgrade rustls-webpki to 0.100.2 or later
   • Upgrade rustls-webpki to 0.101.4 or later

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