Impact go-git may parse malformed Git objects in a way that differs from upstream Git. When commit or tag objects contain ambiguous or malformed headers, go-git’s decoded representation may expose values differently from how Git itself would interpret or reject the same object.

Additionally, go-git’s commit signing and verification logic operates over commit data reconstructed from go-git’s parsed representation rather than the original raw object bytes. As a result, go-git may sign or verify a commit payload that is not byte-for-byte equivalent to the object stored in the repository.

This can cause a signature to appear valid for a commit whose displayed or effective metadata differs from the object that was intended to be signed.

Patches Users should upgrade to a patched version in order to mitigate this vulnerability. Versions prior to v5 are likely to be affected, users are recommended to upgrade to a supported go-git version.

Credit

Thanks to @bugbunny-research (https://bugbunny.ai/) for reporting this to sigstore/gitsign, and to @wlynch, @patzielinski and @adityasaky for coordinating the disclosure with the go-git project. :bow: :1stplacemedal:

Thanks to @wayphinder for reporting this to the go-git project. :bow:

Impact A path validation issue in go-git could allow crafted repository data to affect files outside the intended checkout target, including the repository's .git directory.

These validations were introduced in upstream Git years ago, so the vulnerability arose from go-git drifting from those checks. Some attack vectors were platform-specific: certain payloads affected only Windows users, others affected only macOS users, and some applied across all supported platforms.

Using non-descendant go-billy filesystem instances, or different filesystem types, for the Storer and Worktree may provide some isolation against .git directory manipulation. For example, users that store the .git directory through memfs while using osfs for the worktree are not affected by this vulnerability in the main repository, because repository metadata is not materialized inside the worktree filesystem.

However, this isolation does not necessarily apply when the repository contains submodules, since submodule dotgit directories may still be represented or materialized within the worktree context.

It is important to note that exploitation requires a maliciously crafted repository payload. Users should always exercise caution when interacting with repositories or Git servers they do not trust.

Patches Users should upgrade to a patched version in order to mitigate this vulnerability. Versions prior to v5 are likely to be affected, users are recommended to upgrade to a supported go-git version.

Credits Thanks to @kodareef5, @AyushParkara and @N0zoM1z0 for reporting this to the go-git project in three separate reports. 🙇

Impact

go-git's SSH transport constructs the remote exec command by wrapping the repository path in single quotes without escaping single quotes embedded inside the path. This diverges from canonical Git, which shell-quotes the path through sqquotebuf so that an embedded ' becomes the '\'' close-escape-reopen sequence and the whole path round-trips as a single quoted argument.

A repository path containing a single quote can therefore break out of the quoted region in the exec command and be appended as additional shell tokens. On SSH servers that evaluate the exec command through a shell (for example a user account whose login shell is /bin/sh or /bin/bash, or a ForceCommand wrapper that re-evaluates $SSHORIGINALCOMMAND), those additional tokens execute in that account's command-execution context. SSH servers that tokenize the exec command without shell evaluation, including the canonical git-shell setup, are not affected.

The vulnerable behaviour is on the SSH server side, not in go-git: the same bytes can be produced by any SSH client. The change in go-git is defense-in-depth that restores parity with canonical Git's wire format and prevents go-git from being a vehicle for reaching shell-evaluating servers through attacker-influenced repository paths.

Patches

Users should upgrade to a patched version in order to mitigate this issue. The fix ports sqquotebuf from canonical Git into go-git's SSH transport so that the wire output is byte-identical to what git itself would send for the same input.

Versions prior to v5 are likely to be affected, users are recommended to upgrade to a supported go-git version.

Credit

Thanks to @N0zoM1z0 for reporting this to the go-git project. :bow: