CVE-2026-34243 — wenxian
CRITICALCVE-2026-34243 is a critical-severity (CVSS 9.8) CWE-77 vulnerability in njzjz/wenxian. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.
wenxian: Command Injection in GitHub Actions Workflow via `issue_comment.body`
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34243.
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
njzjz/wenxianReal-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
A GitHub Actions workflow uses untrusted user input from issue_comment.body directly inside a shell command, allowing potential command injection and arbitrary code execution on the runner.
Details
The workflow is triggered by issue_comment, which can be controlled by external users.
In the following step:
echo identifiers=$(echo "${{ github.event.comment.body }}" | grep -oE '@njzjz-bot .*' | head -n1 | cut -c12- | xargs) >> $GITHUB_OUTPUT
the value of github.event.comment.body is directly interpolated into a shell command inside run:.
Since GitHub Actions evaluates ${{ }} before execution, attacker-controlled input is injected into the shell context without sanitization. This creates a command injection risk.
Additionally, the extracted value is later reused in another step that constructs output using backticks:
echo '@${{ github.event.comment.user.login }} Here is the BibTeX entry for `${{ steps.extract-identifiers.outputs.identifiers }}`:'
which may further propagate unsafe content.
PoC
- Go to an issue in the repository
- Post a comment such as:
@njzjz-bot paper123" ) ; whoami ; #
- Observe whether the command is executed or reflected in logs/output <img width="658" height="203" alt="poc" src="https://github.com/user-attachments/assets/084ac264-8cb9-4721-8279-26a1da9b891f" />
The injected payload successfully breaks out of the quoted context and executes arbitrary shell commands.
As shown in the workflow logs, the injected whoami command is executed, and the output (runner) is printed. This confirms that attacker-controlled input from github.event.comment.body is interpreted as shell commands.
This demonstrates a clear command injection vulnerability in the workflow.
Impact
-
Remote attackers can inject arbitrary shell commands via issue comments
-
Potential impacts:
- Execution of arbitrary commands in GitHub Actions runner
- Access to
GITHUB_TOKEN - Exfiltration of repository data
- CI/CD pipeline compromise
This issue affects all current versions of the repository as the vulnerable workflow is present in the main branch.
Suggested Fix
Avoid directly interpolating untrusted user input into shell commands.
Instead, pass github.event.comment.body through an environment variable and reference it safely within the script:
- name: Extract identifiers
id: extract-identifiers
env:
COMMENT_BODY: ${{ github.event.comment.body }}
run: |
identifiers=$(echo "$COMMENT_BODY" | grep -oE '@njzjz-bot .*' | head -n1 | cut -c12- | xargs)
echo "identifiers=$identifiers" >> $GITHUB_OUTPUT
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦GitHub Actions | njzjz/wenxian | all versions | No fix |
Affected Products
wenxiannjzjzDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for njzjz/wenxian, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of njzjz/wenxian for CVE-2026-34243. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
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-2026-34243 in your dependencies?
Find it across GitHub Actions, including transitive dependencies.