CVE-2026-25934

Workarounds

In case updating to a fixed version of go-git is not possible, users can run git fsck from the git cli to check for data corruption on a given repository.

Credit

Thanks @N0zoM1z0 for finding and reporting this issue privately to the go-git project.

A vulnerability was discovered in go-git whereby data integrity values for .pack and .idx files were not properly verified. This resulted in go-git potentially consuming corrupted files, which would likely result in unexpected errors such as object not found.

For context, clients fetch packfiles from upstream Git servers. Those files contain a checksum of their contents, so that clients can perform integrity checks before consuming it. The pack indexes (.idx) are generated locally by go-git, or the git cli, when new .pack files are received and processed. The integrity checks for both files were not being verified correctly.

Note that the lack of verification of the packfile checksum has no impact on the trust relationship between the client and server, which is enforced based on the protocol being used (e.g. TLS in the case of https:// or known hosts for ssh://). In other words, the packfile checksum verification does not provide any security benefits when connecting to a malicious or compromised Git server.

CVE-2026-25934 has a CVSS score of 4.3 (Medium). The vector is network-reachable, no privileges required, and user interaction required. 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 (5.16.5); upgrading removes the vulnerable code path.

Kodem intelligence

Users should upgrade to v5.16.5, or the latest v6 pseudo-version, in order to mitigate this vulnerability.

1. What is CVE-2026-25934? CVE-2026-25934 is a medium-severity security vulnerability in github.com/go-git/go-git/v5 (go), affecting versions <= 5.16.4. It is fixed in 5.16.5.
2. How severe is CVE-2026-25934? CVE-2026-25934 has a CVSS score of 4.3 (Medium). 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 github.com/go-git/go-git/v5 are affected by CVE-2026-25934? github.com/go-git/go-git/v5 (go) versions <= 5.16.4 is affected.
4. Is there a fix for CVE-2026-25934? Yes. CVE-2026-25934 is fixed in 5.16.5. Upgrade to this version or later.
5. Is CVE-2026-25934 exploitable, and should I be worried? Whether CVE-2026-25934 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 CVE-2026-25934 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 CVE-2026-25934? Upgrade github.com/go-git/go-git/v5 to 5.16.5 or later.