GHSA-R4FJ-R33X-8V88
Vulnerability from github – Published: 2026-03-29 15:39 – Updated: 2026-03-31 18:54Summary
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
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:
```yaml - 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" >> $GITHUB_OUTPUT
{
"affected": [
{
"package": {
"ecosystem": "GitHub Actions",
"name": "njzjz/wenxian"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "0.3.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-34243"
],
"database_specific": {
"cwe_ids": [
"CWE-20",
"CWE-77",
"CWE-78"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-29T15:39:56Z",
"nvd_published_at": "2026-03-31T16:16:33Z",
"severity": "CRITICAL"
},
"details": "#### Summary\n\nA GitHub Actions workflow uses untrusted user input from `issue_comment.body` directly inside a shell command, allowing potential command injection and arbitrary code execution on the runner.\n\n#### Details\n\nThe workflow is triggered by `issue_comment`, which can be controlled by external users.\nIn the following step:\n\n```bash\necho identifiers=$(echo \"${{ github.event.comment.body }}\" | grep -oE \u0027@njzjz-bot .*\u0027 | head -n1 | cut -c12- | xargs) \u003e\u003e $GITHUB_OUTPUT\n```\n\nthe value of `github.event.comment.body` is directly interpolated into a shell command inside `run:`.\n\nSince GitHub Actions evaluates `${{ }}` before execution, attacker-controlled input is injected into the shell context without sanitization. This creates a command injection risk.\n\nAdditionally, the extracted value is later reused in another step that constructs output using backticks:\n\n```bash\necho \u0027@${{ github.event.comment.user.login }} Here is the BibTeX entry for `${{ steps.extract-identifiers.outputs.identifiers }}`:\u0027\n```\n\nwhich may further propagate unsafe content.\n\n#### PoC\n\n1. Go to an issue in the repository\n2. Post a comment such as:\n\n`@njzjz-bot paper123\" ) ; whoami ; #\n`\n\n3. Observe whether the command is executed or reflected in logs/output\n\u003cimg width=\"658\" height=\"203\" alt=\"poc\" src=\"https://github.com/user-attachments/assets/084ac264-8cb9-4721-8279-26a1da9b891f\" /\u003e\n\nThe injected payload successfully breaks out of the quoted context and executes arbitrary shell commands.\n\nAs 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.\n\nThis demonstrates a clear command injection vulnerability in the workflow.\n\n#### Impact\n\n* Remote attackers can inject arbitrary shell commands via issue comments\n* Potential impacts:\n\n * Execution of arbitrary commands in GitHub Actions runner\n * Access to `GITHUB_TOKEN`\n * Exfiltration of repository data\n * CI/CD pipeline compromise\n\n\nThis issue affects all current versions of the repository as the vulnerable workflow is present in the main branch.\n\n### Suggested Fix\n\nAvoid directly interpolating untrusted user input into shell commands.\n\nInstead, pass `github.event.comment.body` through an environment variable and reference it safely within the script:\n\n```yaml\n- name: Extract identifiers\n id: extract-identifiers\n env:\n COMMENT_BODY: ${{ github.event.comment.body }}\n run: |\n identifiers=$(echo \"$COMMENT_BODY\" | grep -oE \u0027@njzjz-bot .*\u0027 | head -n1 | cut -c12- | xargs)\n echo \"identifiers=$identifiers\" \u003e\u003e $GITHUB_OUTPUT",
"id": "GHSA-r4fj-r33x-8v88",
"modified": "2026-03-31T18:54:46Z",
"published": "2026-03-29T15:39:56Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/njzjz/wenxian/security/advisories/GHSA-r4fj-r33x-8v88"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34243"
},
{
"type": "PACKAGE",
"url": "https://github.com/njzjz/wenxian"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "wenxian: Command Injection in GitHub Actions Workflow via `issue_comment.body` "
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.