CVE-2026-122299
Description
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.
Statement
This vulnerability is rated as an Important severity risk because successful exploitation can result in full code execution on build systems or developer workstations, though it requires tricking a user or pipeline into processing an untrusted Git dependency. In typical Red Hat deployments, Dulwich is not run as an exposed network service, but rather operates within development environments or packaging toolchains to handle repository operations. Because Dulwich resolves duplicated tree definitions differently from reference Git implementations, malicious payloads can bypass standard code review or CI audit checks, making this a high-impact supply chain concern.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
--- CME Mitigation Guidance (2026-11-06) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to ensure Git commit parsing enforces strict tree header ordering and single-occurrence resolution across all repository processing tools: upgrade to Dulwich 1.2.20 (or the corresponding fixed Red Hat builds), which require the tree header first, resolve only the first occurrence of repeated commit and tag headers, and reject commits and tags that core Git refuses to parse, closing all 2 injection vectors (crafted Git commit object with duplicate tree headers, dependency installation using Dulwich-based package managers). Until patched, this is a concern on Developer workstations and build systems processing untrusted Git repositories via Dulwich or Dulwich-dependent tools, so Avoid resolving dependencies from untrusted Git repositories in automated CI/CD pipelines and developer environments using Dulwich-dependent tools like Poetry. As a compensating measure, Restrict outbound network traffic from build hosts to contain C2 communication and payload retrieval, Enforce WDAC in enforced mode to block unauthorized binaries and scripts introduced by the malicious tree, Deploy EDR agents to detect anomalous child processes and system activity spawned by executed build scripts, Configure auditd to log execve syscalls and process execution events on Linux build systems, and Use Falco or eBPF runtime security to detect anomalous shell spawns and unexpected outbound network traffic in CI/CD containers. These controls limit blast radius and contain exploitation, but they do not fix the underlying duplicate tree header parser differential — apply the upstream patch to fully remediate.
Highest-impact CME: CME-925 Windows Defender Application Control (WDAC) (medium)
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.8 | N/A | 8.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Unexpected State
Frequently Asked Questions
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