Vulnerability in Jelmer Dulwich
CVE-2026-122299
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.003 (25.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 25.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
The 30-day trend appears once there are two daily scores.
Affected products
Weakness classification (CWE)
References
- github.com/jelmer/dulwich/commit/b77f385b4b0d2d2c7f5ac39dae628948f7ad3a96 (issue-tracking, patch)
- github.com/jelmer/dulwich/releases/tag/dulwich-1.2.20 (release-notes, patch)
- www.vulncheck.com/advisories/dulwich-before-commit-parser-tree-header-misinterp… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-122299?
- CVE-2026-122299 is a high-severity vulnerability in Jelmer Dulwich, classified under CWE-115. CVSS score: 8.8/10. Published 2026-11-04.
- How severe is CVE-2026-122299?
- High severity. CVSS v3 base score is 8.8 out of 10.