Dulwich: Arbitrary file write via DOS drive letter paths on Windows
Summary
Dulwich, a Python Git library, does not reject Git tree entries that start with a DOS drive letter such as 'C:' on Windows. A malicious repository can therefore make Dulwich write files outside the worktree, for example into user profile or startup folders. Successful exploitation can lead to remote code execution, but the victim must clone or check out the attacker-controlled repository on a Windows host.
Affected
- Dulwich versions before 1.2.9 on Windows
- Linux and macOS hosts are not affected by this mechanism
Fixed in
- Dulwich 1.2.9
- No distribution-specific fixed version identified; Ubuntu lists dulwich as 'Needs evaluation'.
Workaround
- No vendor-published workaround. Upgrading to Dulwich 1.2.9 or later is the remedy.
- Where an upgrade is not yet possible, do not clone or check out untrusted repositories on Windows hosts or CI runners.
Exploitation
- Known exploited: no (no CISA KEV listing found as of 1 Nov 2026).
- Public proof of concept: the GHSA entry includes a reproducer.
- CISA SSVC: exploitation status 'poc', automatable: no, technical impact: total.
Our recommendation
- Inventory Python environments and tools that bundle Dulwich, especially on Windows machines and build agents.
- Update Dulwich to version 1.2.9 or later.
- Avoid cloning untrusted repositories on Windows hosts or CI runners until updated.
- Monitor for unexpected file writes outside project directories on Windows systems.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-8mcx-5rqc-vhmf github.com
- VulnCheck advisory www.vulncheck.com
- OSV GHSA-8mcx-5rqc-vhmf osv.dev
- GitLab Advisory Database entry advisories.gitlab.com
- Ubuntu CVE tracker ubuntu.com
- OpenCVE CVE-2026-114094 app.opencve.io
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 01:10.
Original description (NVD)
Dulwich before 1.2.9 fails to validate DOS drive letter prefixes in Git tree path elements on Windows, allowing arbitrary file write. Attackers can craft a malicious repository with a tree entry named 'C:' that bypasses NTFS validation and writes files outside the worktree to achieve remote code execution.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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