Summary
tj-actions/changed-files has Potential Actions command injection in output filenames (GHSL-2023-271)
The tj-actions/changed-files workflow allows for command injection in changed filenames, allowing an attacker to execute arbitrary code and potentially leak secrets.
Details
The changed-files action returns a list of files changed in a commit or pull request which provides an escape_json input enabled by default, only escapes " for JSON values.
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 a repository with a new file injecting a command. For example
$(whoami).txtwhich is 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 filesstep below.
- name: List all changed files
run: |
for file in ${{ steps.changed-files.outputs.all_changed_files }}; do
echo "$file was changed"
done
Example output:
##[group]Run for file in $(whoami).txt; do
for file in $(whoami).txt; do
echo "$file was changed"
done
shell: /usr/bin/bash -e {0}
##[endgroup]
runner.txt was changed
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
env:
ALL_CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files }}
run: |
for file in "$ALL_CHANGED_FILES"; do
echo "$file was changed"
done
Resources
Impact
This issue may lead to arbitrary command execution in the GitHub Runner.
Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command. Typical impact: arbitrary command execution in the application's environment.
CVE-2023-51664 has a CVSS score of 7.3 (High). The vector is network-reachable, low privileges required, and user interaction required. 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 (41); 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.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2023-51664? CVE-2023-51664 is a high-severity command injection vulnerability in tj-actions/changed-files (actions), affecting versions < 41. It is fixed in 41. Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command.
- How severe is CVE-2023-51664? CVE-2023-51664 has a CVSS score of 7.3 (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/changed-files are affected by CVE-2023-51664? tj-actions/changed-files (actions) versions < 41 is affected.
- Is there a fix for CVE-2023-51664? Yes. CVE-2023-51664 is fixed in 41. Upgrade to this version or later.
- Is CVE-2023-51664 exploitable, and should I be worried? Whether CVE-2023-51664 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-2023-51664 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-2023-51664? Upgrade
tj-actions/changed-filesto 41 or later.