CVE-2026-114094 in Dulwich
Summary
by MITRE • 10/21/2026
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.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified in versions of Dulwich prior to 1.2.9 represents a critical security flaw rooted in improper input validation within the Git repository parsing logic on Windows operating systems. Dulwich is a pure Python implementation of the Git protocol, widely used for interacting with Git repositories without relying on external binaries. The core issue lies in how the library processes tree entries during clone or fetch operations. Specifically, when encountering path elements that resemble DOS drive letter prefixes, such as C:, the software fails to perform adequate sanitization checks against NTFS file system constraints and working directory boundaries. This oversight allows an attacker to manipulate the internal representation of file paths within a malicious repository structure.
In standard Git workflows on Windows, tree entries define the relative path where files should be checked out or stored during operations like cloning. Under normal circumstances, these paths are resolved relative to the target worktree root to ensure that all extracted files remain contained within the designated directory structure. However, due to this validation gap, a crafted repository can include a blob entry with a name starting with a drive letter followed by a colon. When Dulwich processes such an entry on Windows, it incorrectly interprets or passes through this prefix without recognizing it as an absolute path indicator that should be rejected or strictly constrained. This behavior effectively bypasses the standard relative-path resolution mechanisms designed to prevent directory traversal attacks.
The operational impact of this flaw is severe, leading directly to arbitrary file write capabilities for any user who clones or fetches from a malicious repository hosted on a Windows system with an affected version of Dulwich. By specifying a target path that includes a valid drive letter and a writable location outside the intended worktree, such as C:\Windows\System32\drivers\etc\hosts or other critical system directories, an attacker can overwrite existing files or create new executable binaries in sensitive locations. This capability transforms what might otherwise be a data integrity issue into a full remote code execution vector if the attacker places malicious scripts or executables in paths that are automatically executed by the operating system or user applications upon access or startup.
This vulnerability aligns with CWE-22, which describes Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal. Furthermore, it relates to CWE-94, specifically improper control of generation of code or commands where untrusted input is used without validation. In the context of the MITRE ATT&CK framework, this exploit technique falls under T1053 Scheduled Task/Job: Local Job and potentially T1204 User Execution if the written files are designed to be triggered by user interaction. The lack of strict boundary enforcement allows the attacker to bypass local security controls that rely on working directory isolation.
To mitigate this risk, organizations relying on Dulwich for Git operations must upgrade immediately to version 1.2.9 or later, where these validation checks have been implemented and tested against various edge cases involving Windows path syntax. For environments unable to update instantly, implementing network-level filtering to block access to untrusted repositories is a recommended interim measure. Additionally, security teams should audit their CI/CD pipelines and automated scripts that utilize Dulwich to ensure they are not processing content from potentially compromised sources without additional sandboxing or strict path validation layers applied externally by the hosting infrastructure.