jelmer Dulwich up to 1.2.19 Commit Object Parser _parse_commit input validation

Summaryinfo

A vulnerability labeled as critical has been found in jelmer Dulwich up to 1.2.19. The affected element is the function _parse_commit of the component Commit Object Parser. Such manipulation leads to input validation. This vulnerability is traded as CVE-2026-122299. The attack may be launched remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in jelmer Dulwich up to 1.2.19 and classified as critical. Affected by this issue is the function _parse_commit of the component Commit Object Parser. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-122299 since 11/04/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit.

Upgrading to version 1.2.20 eliminates this vulnerability.

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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
• 1.2.5
• 1.2.6
• 1.2.7
• 1.2.8
• 1.2.9
• 1.2.10
• 1.2.11
• 1.2.12
• 1.2.13
• 1.2.14
• 1.2.15
• 1.2.16
• 1.2.17
• 1.2.18
• 1.2.19

Website

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

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