CVE-2026-42563

Dulwich is a pure-Python implementation of the Git file formats and protocols. Starting in version 0.24.0 and prior to version 1.2.5, Dulwich's `ProcessMergeDriver` substitutes the file path (from the git tree, controllable by an attacker via a malicious branch) into the merge driver command via the `%P` placeholder and executes it with `subprocess.run(..., shell=True)`. An attacker who can cause a victim to merge an untrusted branch can achieve arbitrary command execution by crafting malicious file paths. Version 1.2.5 fixes the issue.

• https://github.com/jelmer/dulwich/commit/e3331b3b3a122fc313460182f928f59723580b7b
• https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5
• https://github.com/jelmer/dulwich/security/advisories/GHSA-9277-mp7x-85jf