Summary
Potential Actions command injection in output filenames (GHSL-2023-275)
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
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
Impact
This issue may lead to arbitrary command execution in the GitHub Runner.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
CVE-2023-52137 has a CVSS score of 7.7 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (17); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2023-52137? CVE-2023-52137 is a high-severity improper input validation vulnerability in tj-actions/verify-changed-files (actions), affecting versions < 17. It is fixed in 17. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is CVE-2023-52137? CVE-2023-52137 has a CVSS score of 7.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of tj-actions/verify-changed-files are affected by CVE-2023-52137? tj-actions/verify-changed-files (actions) versions < 17 is affected.
- Is there a fix for CVE-2023-52137? Yes. CVE-2023-52137 is fixed in 17. Upgrade to this version or later.
- Is CVE-2023-52137 exploitable, and should I be worried? Whether CVE-2023-52137 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-52137 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-52137? Upgrade
tj-actions/verify-changed-filesto 17 or later.