# CVE-2026-122299: Dulwich before 1.2.20 Commit Parser Tree Header Misinterpretation


- **Severity:** High 8.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 4 Nov 2026
- **Updated:** 9 Nov 2026
- **Also known as:** AZL-112720, DEBIAN-CVE-2026-122299, GHSA-6jv4-m4h7-2vv8, UBUNTU-CVE-2026-122299

## What is CVE-2026-122299?

CVE-2026-122299 is a high-severity vulnerability in jelmer dulwich, published on 4 Nov 2026. 

### 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.

Weakness: CWE-1250 (Improper Preservation of Consistency Between Independent Representations of Shared State), CWE-115 (Misinterpretation of Input)

## Which versions are affected by CVE-2026-122299?


## How do I fix CVE-2026-122299?

No fix has been published for CVE-2026-122299 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-122299 being exploited?

There is no known exploitation of CVE-2026-122299 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-122299 and fix it if it is affected.

What it is: CVE-2026-122299 is a high-severity vulnerability in jelmer dulwich, published on 4 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-122299 in the wild and no public exploit code.

Affected product: jelmer dulwich. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-122299/ (Markdown: https://insights.sbomify.com/CVE-2026-122299/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-122299
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-122299
- OSV: https://osv.dev/vulnerability/CVE-2026-122299

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-122299/
Summaries are generated and may contain mistakes; the official description above is the record.