CVE-2026-42563
CVE-2026-42563 is a high-severity vulnerability with a CVSS 4.0 base score of 7.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-78.
Key facts
- Severity: High (CVSS 4.0 base score 7.7)
- EPSS exploit prediction: 1% (42nd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-36175
- Weakness: CWE-78
- Published:
- Last modified:
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.
Frequently asked questions
- What is 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.
- How severe is CVE-2026-42563?
- CVE-2026-42563 has a CVSS 4.0 base score of 7.7, rated high severity.
- Is CVE-2026-42563 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-42563?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2026-42563 have an EU (EUVD) identifier?
- Yes. CVE-2026-42563 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-36175.
- When was CVE-2026-42563 published?
- CVE-2026-42563 was published on 2026-06-10 and last updated on 2026-06-17.
References
- 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
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