CVE-2023-52137 is a high-severity (CVSS 7.7) Improper Input Validation vulnerability in tj-actions/verify-changed-files. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for tj-actions/verify-changed-files — see the affected versions and patch details below.
GitHub Action tj-actions/verify-changed-files is vulnerable to command injection in output filenames
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
tj-actions/verify-changed-filesReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects GitHub Actions packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The tj-actions/verify-changed-files action allows for command injection in changed filenames, allowing an attacker to execute arbitrary code and potentially leak secrets.
Details
The verify-changed-files workflow returns the list of files changed within a workflow execution.
This could potentially allow filenames that contain special characters such as ; and ` (backtick) which can be used by an attacker to take over the GitHub Runner if the output value is used in a raw fashion (thus being directly replaced before execution) inside a run block. By running custom commands an attacker may be able to steal secrets such as GITHUB_TOKEN if triggered on other events than pull_request. For example on push.
Proof of Concept
- Submit a pull request to the repository with a new file injecting a command. For example
$(whoami).txtwould be a valid filename. - Upon approval of the workflow (triggered by the pull request), the action will get executed and the malicious pull request filename will flow into the
List all changed files tracked and untracked filesstep.
- name: List all changed files tracked and untracked files
run: |
echo "Changed files: ${{ steps.verify-changed-files.outputs.changed_files }}"
Example output:
##[group]Run echo "Changed files: $(whoami).txt"
echo "Changed files: $(whoami).txt"[0m
shell: /usr/bin/bash -e {0}
##[endgroup]
Changed files: runner.txt
Impact
This issue may lead to arbitrary command execution in the GitHub Runner.
Resolution
-
A new
safe_outputinput would be enabled by default and return filename paths escaping special characters like ;, ` (backtick), $, (), etc for bash environments. -
A safe recommendation of using environment variables to store unsafe outputs.
- name: List all changed files tracked and untracked files
env:
CHANGED_FILES: ${{ steps.verify-changed-files.outputs.changed_files }}
run: |
echo "Changed files: $CHANGED_FILES"
Resources
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦GitHub Actions | tj-actions/verify-changed-files | all versions | 17 |
Affected Products
verify-changed-filestj-actionsResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tj-actions/verify-changed-files, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update tj-actions/verify-changed-files to 17 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-52137 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.
Frequently Asked Questions
Is CVE-2023-52137 in your dependencies?
Find it across GitHub Actions, including transitive dependencies.