Summary
PyPI publish GitHub Action vulnerable to injectable expression expansions in action steps
gh-action-pypi-publish makes use of GitHub Actions expression expansions (i.e. ${{ ... }}) in contexts that are potentially attacker controllable. Depending on the trigger used to invoke gh-action-pypi-publish, this may allow an attacker to execute arbitrary code within the context of a workflow step that invokes gh-action-pypi-publish.
Details
gh-action-pypi-publish contains a composite action step, set-repo-and-ref, that makes use of expression expansions:
- name: Set repo and ref from which to run Docker container action
id: set-repo-and-ref
run: |
# Set repo and ref from which to run Docker container action
# to handle cases in which `github.action_` context is not set
# https://github.com/actions/runner/issues/2473
REF=${{ env.ACTION_REF || env.PR_REF || github.ref_name }}
REPO=${{ env.ACTION_REPO || env.PR_REPO || github.repository }}
REPO_ID=${{ env.PR_REPO_ID || github.repository_id }}
echo "ref=$REF" >>"$GITHUB_OUTPUT"
echo "repo=$REPO" >>"$GITHUB_OUTPUT"
echo "repo-id=$REPO_ID" >>"$GITHUB_OUTPUT"
shell: bash
env:
ACTION_REF: ${{ github.action_ref }}
ACTION_REPO: ${{ github.action_repository }}
PR_REF: ${{ github.event.pull_request.head.ref }}
PR_REPO: ${{ github.event.pull_request.head.repo.full_name }}
PR_REPO_ID: ${{ github.event.pull_request.base.repo.id }}
In normal intended operation, these expansions are used to establish a correct priority for outputs like ref and repo-id.
However, these expansions have a side effect: because they're done with ${{ ... }} and not with ${...} (i.e. normal shell interpolation), they can bypass normal shell quoting rules. In particular, if both env.ACTION_REF and env.PR_REF evaluate to empty strings, then the expression falls back to github.ref_name, which can be an attacker controlled string via a branch or tag name.
For example, if the attacker is able to set a branch name to something like innocent;cat${IFS}/etc/passwd, then the REF line may expand as:
REF=innocent;cat${IFS}/etc/passwd
which would set REF to innocent and then run the attacker's code.
Additional information about dangerous expansions can be found in zizmor's template-injection rule documentation.
Impact
The impact of this vulnerability is very low: the expression in question is unlikely to be evaluated in normal operation, since env.ACTION_REF should always take precedence.
In particular, the action is not vulnerable in many popular configurations, i.e. those where pull_request or release or a push: tags event is used to call the action.
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.
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 GHSA-VXMW-7H4F-HQXH? GHSA-VXMW-7H4F-HQXH is a low-severity command injection vulnerability in pypa/gh-action-pypi-publish (actions), affecting versions < 1.13.0. It is fixed in 1.13.0. Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command.
- Which versions of pypa/gh-action-pypi-publish are affected by GHSA-VXMW-7H4F-HQXH? pypa/gh-action-pypi-publish (actions) versions < 1.13.0 is affected.
- Is there a fix for GHSA-VXMW-7H4F-HQXH? Yes. GHSA-VXMW-7H4F-HQXH is fixed in 1.13.0. Upgrade to this version or later.
- Is GHSA-VXMW-7H4F-HQXH exploitable, and should I be worried? Whether GHSA-VXMW-7H4F-HQXH 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 GHSA-VXMW-7H4F-HQXH 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 GHSA-VXMW-7H4F-HQXH? Upgrade
pypa/gh-action-pypi-publishto 1.13.0 or later.