CVE-2026-42563
HighCVSS 7.7Exploitation Probability (EPSS)
Low risk43th percentile - higher than 43% of all known CVEs
Summary
A vulnerability in the Dulwich library (versions 0.24.0 through 1.2.4) allows arbitrary command execution. An attacker can craft a malicious file path in a Git branch, which is substituted into the merge driver command via the %P placeholder and executed with shell=True when a victim merges the branch.
Risk Assessment
The risk is that an attacker can execute arbitrary commands on the victim's system in the context of the user performing the merge. This could lead to data theft, malware installation, or further privilege escalation.
Recommendation
Immediately update Dulwich to version 1.2.5 or later. If an update is not possible, avoid merging branches from untrusted sources.
Other vulnerabilities in Dulwich
See all- CVE-2015-0838High
Buffer overflow in the C implementation of the apply_delta function in _pack.c in Dulwich before version 0.9.9 allows remote attackers to execute arbitrary code via a crafted pack file.
- CVE-2014-9706High
The build_index_from_tree function in index.py in Dulwich before version 0.9.9 allows remote attackers to execute arbitrary code via a commit with a directory path starting with .git/, which is not properly handled when checking out a working tree.
- CVE-2017-16228Critical
Dulwich before version 0.18.5, when using an SSH subprocess, allows remote attackers to execute arbitrary commands via an ssh URL with an initial dash character in the hostname.
- CVE-2026-38974Medium
Dulwich through version 1.1.0 is missing SSH host key verification in contrib/paramiko_vendor.py. This means that during SSH connections, the server's public key is not checked for trustworthiness.
- CVE-2026-52726High
Dulwich versions 0.23.2 through 1.2.5 do not validate submodule paths during recursive clone. An attacker can craft a malicious .gitmodules and gitlink tree with path .git/hooks, causing files to be written into the victim's .git/hooks directory. Executable files are then run on any hook invocation, leading to remote code execution.
- CVE-2026-47734Medium
A vulnerability in Dulwich (versions 0.1.0 through 1.2.4) allows a client with push access to send a crafted thin pack (~174 bytes) whose delta header declares a huge dest_size. When processed by add_thin_pack/apply_delta, it allocates hundreds of MB of memory, potentially causing resource exhaustion.
- CVE-2026-47712Low
A vulnerability in Dulwich (versions 0.24.0 through 1.2.4) allows writing patch files outside the intended directory via a malicious commit subject. The format_patch function derives filenames from commit subjects without sanitizing path separators or parent-directory components.
- CVE-2026-42305High
A vulnerability in the Dulwich library (versions 0.10.0 through 1.2.4) allows remote code execution via arbitrary file write when cloning or checking out a malicious Git repository on Windows. The issue stems from improper validation of path elements that can contain bytes interpreted by Windows as structural path syntax. Additionally, the core.protectNTFS and core.protectHFS security settings were silently ignored due to configuration bugs.
Original NVD description (English source)
Dulwich is a pure-Python implementation of the Git file formats and protocols. Starting in version 0.24.0 and prior to version 1.2.5, Dulwich's `ProcessMergeDriver` substitutes the file path (from the git tree, controllable by an attacker via a malicious branch) into the merge driver command via the `%P` placeholder and executes it with `subprocess.run(..., shell=True)`. An attacker who can cause a victim to merge an untrusted branch can achieve arbitrary command execution by crafting malicious file paths. Version 1.2.5 fixes the issue.