jelmer dulwich up to 1.2.4 Merge Driver Command os command injection

Summaryinfo

A vulnerability was found in jelmer dulwich up to 1.2.4. It has been declared as critical. The impacted element is an unknown function of the component Merge Driver Command Handler. The manipulation results in os command injection. This vulnerability was named CVE-2026-42563. The attack may be performed from remote. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in jelmer dulwich up to 1.2.4. Affected is some unknown processing of the component Merge Driver Command Handler. The manipulation with an unknown input leads to a os command injection vulnerability. CWE is classifying the issue as CWE-78. The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-42563 since 04/28/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1202 by the MITRE ATT&CK project.

Upgrading to version 1.2.5 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch e3331b3b3a122fc313460182f928f59723580b7b is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• jelmer

Name

• dulwich

Version

• 1.2.0
• 1.2.1
• 1.2.2
• 1.2.3
• 1.2.4

License

• open-source

Website

• Product: https://github.com/jelmer/dulwich/

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