Summary
sequoia-git has broken hard revocation handling
Before sq-git checks if a commit can be authenticated, it first looks for hard revocations. Because parsing a policy is expensive
and a project's policy rarely changes, sq-git has an optimization to only check a policy if it hasn't checked it before. It does this by maintaining a set of policies that it had already seen keyed on the policy's hash. Unfortunately, due to a bug the hash was truncated to be 0 bytes and thus only hard revocations in the target commit were considered. Normally this is not a problem as hard revocations are not removed from the signing policy.
An attacker could nevertheless exploit this flaw as follows. Consider Alice and Bob who maintain a project together. If Bob's
certificate is compromised and Bob issues a hard revocation, Alice can add it to the project's signing policy. An attacker who has
access to Bob's key can then create a merge request that strips the hard revocation. If Alice merges Bob's merge request, then
the latest commit will not carry the hard revocation, and sq-git will not see the hard revocation when authenticating that commit or any following commits.
Note: for this attack to be successful, Alice needs to be tricked into merging the malicious MR. If Alice is reviewing MRs, then she is likely to notice changes to the signing policy.
Reported-by: Hassan Sheet
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is GHSA-G27R-R6PH-VF5R? GHSA-G27R-R6PH-VF5R is a low-severity security vulnerability in sequoia-git (rust), affecting versions < 0.6.0. It is fixed in 0.6.0.
- Which versions of sequoia-git are affected by GHSA-G27R-R6PH-VF5R? sequoia-git (rust) versions < 0.6.0 is affected.
- Is there a fix for GHSA-G27R-R6PH-VF5R? Yes. GHSA-G27R-R6PH-VF5R is fixed in 0.6.0. Upgrade to this version or later.
- Is GHSA-G27R-R6PH-VF5R exploitable, and should I be worried? Whether GHSA-G27R-R6PH-VF5R 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
- What actually determines whether GHSA-G27R-R6PH-VF5R 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.
- How do I fix GHSA-G27R-R6PH-VF5R? Upgrade
sequoia-gitto 0.6.0 or later.