CVE-2026-42563 Dulwich Vulnerable to Command Injection via Merge Driver Path
Attackers can execute arbitrary commands by tricking users into merging malicious branches containing crafted file paths in Dulwich.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-42563?
CVE-2026-42563 is a high-severity command injection vulnerability in jelmer dulwich, published on 10 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-78
Which versions are affected by CVE-2026-42563?
3 open source packages ship an affected version, including dulwich.
| Package | Affected | Fixed in |
|---|---|---|
dulwich PyPI | From 0.24.0 | 1.2.5 |
dulwich PyPI | From 0.24.0 | 1.2.5 |
dulwich PyPI | From 0.24.0 | 1.2.5 |
How do I fix CVE-2026-42563?
Upgrade dulwich to 1.2.5 or later.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is CVE-2026-42563 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42563 exists.
Sources
Also known as CLEANSTART-2026-MJ32285, CLSA-2026-1781052734, DEBIAN-CVE-2026-42563, ECHO-b3a3-3b48-f3fe, GHSA-9277-mp7x-85jf, MINI-2p86-fr3m-g34v and 3 more.