Bug 2567721 (CVE-2026-122299)

Summary: CVE-2026-122299 dulwich: dulwich: Arbitrary code execution via duplicate tree header parsing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, gbenhaim, jdelft, jdobes, jlanda, jmitchel, jupierce, kgaikwad, kshier, lgarciaa, mbiarnes, niyer, orabin, ppalepu, ppostler, prdhamdh, rbobbitt, rhel-process-autobot, sghai, sidsharm, simaishi, stcannon, suppawar, twaugh, vlaad, watson-tool-maintainers, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Dulwich. This flaw allows arbitrary code execution on systems that process untrusted repositories. When parsing Git commit objects, Dulwich resolves duplicate tree headers to the last occurrence instead of the first, conflicting with standard Git behavior. A remote attacker can exploit this issue by crafting a commit with multiple tree headers, causing applications that rely on Dulwich to check out malicious code while standard Git review and continuous integration (CI) systems display benign files.
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Description OSIDB Bzimport 2026-11-05 22:20:43 UTC 
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.