CVE-2026-34243 — njzjz/wenxian
CRITICALCVE-2026-34243 is a critical-severity (CVSS 9.8) CWE-77 vulnerability in njzjz/wenxian. No vendor fix is recorded yet; mitigation options are listed below.
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
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.
How urgent is this, really
CVE-2026-34243 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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 |
Detection & 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
No patched version of njzjz/wenxian has shipped for CVE-2026-34243 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-34243 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-34243. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-34243 in your dependencies?
O3 Security finds CVE-2026-34243 across GitHub Actions dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.