Vulnerability · Published Nov 4, 2026 · Assigned by VulnCheck
CVE-2026-122299Dulwich before 1.2.20 Commit Parser Tree Header Misinterpretation
High 8.8
In plain English
A high-severity security flaw in dulwich from jelmer. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities).
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | dulwich | no fix listed | DEBIAN-CVE-2026-122299 |
| Debian:13 | dulwich | no fix listed | DEBIAN-CVE-2026-122299 |
| Debian:14 | dulwich | no fix listed | DEBIAN-CVE-2026-122299 |
| Ubuntu:22.04:LTS | dulwich | no fix listed | UBUNTU-CVE-2026-122299 |
| Ubuntu:24.04:LTS | dulwich | no fix listed | UBUNTU-CVE-2026-122299 |
| Ubuntu:26.04:LTS | dulwich | no fix listed | UBUNTU-CVE-2026-122299 |
| Ubuntu:26.10 | dulwich | no fix listed | UBUNTU-CVE-2026-122299 |
Affected products (as reported)
Weakness: CWE-1250, CWE-115 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
References
- Vendor Patch patch, release-notes
- https://github.com/jelmer/dulwich/commit/b77f385b4b0d2d2c7f5ac39dae628948f7ad3a96 issue-tracking
- VulnCheck Advisory: Dulwich before 1.2.20 Commit Parser Tree Header Misinterpretation third-party-advisory