Compliance Impact

The vulnerability CVE-2026-42563 allows an attacker to achieve arbitrary command execution on a victim's system by exploiting the Dulwich library's ProcessMergeDriver component. This high-impact security flaw could lead to unauthorized access, data manipulation, or system compromise.

Such unauthorized command execution and potential data breaches could negatively affect compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data and secure system operations.

Organizations using vulnerable versions of Dulwich without applying the patch (version 1.2.5 or later) may face increased risk of non-compliance due to potential data exposure or system integrity violations resulting from exploitation of this vulnerability.

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Executive Summary

This vulnerability exists in Dulwich, a pure-Python implementation of Git file formats and protocols. Specifically, in versions from 0.24.0 up to but not including 1.2.5, the ProcessMergeDriver component substitutes the file path from the git tree into the merge driver command using the %P placeholder. Since the file path can be controlled by an attacker through a malicious branch, this substitution is executed with subprocess.run(..., shell=True), which allows the attacker to execute arbitrary commands on the victim's system when they merge the malicious branch.

The issue is fixed in version 1.2.5.

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Impact Analysis

An attacker who can trick a victim into merging a malicious branch can execute arbitrary commands on the victim's system. This can lead to unauthorized actions such as data theft, system compromise, or further malware installation, depending on the commands executed.

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Mitigation Strategies

To mitigate this vulnerability, upgrade Dulwich to version 1.2.5 or later, where the issue has been fixed.

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Detection Guidance

This vulnerability occurs when the Dulwich library's ProcessMergeDriver uses the %P placeholder in merge driver commands, which can be exploited by malicious file paths during a git merge operation.

To detect if your system is vulnerable, first check the version of Dulwich installed. Versions >=0.24.0 and <1.2.5 are affected.

• Check Dulwich version using Python package management commands, for example: pip show dulwich
• Look for merge drivers configured to use the %P placeholder in your git configuration files (.git/config or system-wide git config). For example, run: git config --list | grep merge
• Audit recent git merges for branches that may contain suspicious or unusual file paths that could be crafted to exploit this vulnerability.

There are no specific network detection commands provided in the resources, but monitoring git merge operations and ensuring no untrusted branches are merged without review is critical.

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