Vulnerabilities

Security incident · CVE-2026-114094

Dulwich: Arbitrary File Write (RCE) on Windows via Unvalidated Drive Letters in Tree Paths

Published Oct 2, 2026 · catalog updated Oct 21, 2026 · Dulwich: Arbitrary File Write

Open the advisory

Exploitation likelihood is not on this record for CVE-2026-114094. A missing EPSS score is not a low risk. Compare Dulwich: Arbitrary File Write with the linked advisory before you change production.

Severity

High8.8

Known exploitation

Not in CISA/VulnCheck KEV

EPSS

Awaiting synchronization with FIRST

Remediation

Advisory link

Affected products

PyPI dulwich

### Affected files * (Methods: , ) * (Method: ) ### Description / Summary A High-severity Path Traversal vulnerability exists in Dulwich's checkout logic when running on Windows. The functions responsible for validating NTFS paths strictly reject variants, Alternate Data Streams (ADS), short names, and reserved device names, but they completely fail to check for **DOS drive letter prefixes**. A malicious Git tree can contain an entry named . When Dulwich processes this tree on a Windows client, the string passes the check. Later, passes this path to . On Windows, if the second argument to contains an absolute drive letter, the path is completely discarded. As a result, Dulwich writes the repository file to the absolute path outside of the intended Git worktree. While the standard C client explicitly blocks this via in , Dulwich lacks this protection. Because Git trees are cross-platform, an attacker can author a malicious repository on Linux and wait for a Windows victim (or CI runner) to clone it. ### Potential impact This vulnerability allows an attacker to achieve **Arbitrary File Write**, which can trivially be escalated to **Remote Code Execution (RCE)** or total system compromise on the victim's Windows machine. Attack vectors include: 1. **Git Config Poisoning (RCE):** Writing a malicious file to set to an arbitrary executable, granting RCE the next time the user interacts with Git. 2. **Persistence (RCE):** Dropping a malicious executable into . 3. **SSH Key Overwrite:** Writing to to compromise remote servers accessible by the victim. 4. **CI/CD Compromise:** If a Windows-based CI/CD runner (e.g., GitHub Actions) automatically clones a malicious pull request, the runner is instantly compromised, potentially leaking repository secrets. ### Proof of Concept (PoC) The following Python script (runnable on Linux) generates a malicious Git repository containing a payload that targets Windows clients.