CVE-2026-34243: wenxian Command Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r4fj-r33x-8v88",
  "modified" : "2026-03-31T18:54:46Z",
  "published" : "2026-03-29T15:39:56Z",
  "aliases" : [ "CVE-2026-34243" ],
  "summary" : "wenxian: Command Injection in GitHub Actions Workflow via `issue_comment.body` ",
  "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 '@njzjz-bot .*' | head -n1 | cut -c12- | xargs) >> $GITHUB_OUTPUT\n```\n\nthe value of `github.event.comment.body` is directly interpolated into a shell command inside `run:`.\n\nSince GitHub Actions evaluates `${{ }}` 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 '@${{ github.event.comment.user.login }} Here is the BibTeX entry for `${{ steps.extract-identifiers.outputs.identifiers }}`:'\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<img width=\"658\" height=\"203\" alt=\"poc\" src=\"https://github.com/user-attachments/assets/084ac264-8cb9-4721-8279-26a1da9b891f\" />\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 \"$COMMENT_BODY\" | grep -oE '@njzjz-bot .*' | head -n1 | cut -c12- | xargs)\n    echo \"identifiers=$identifiers\" >> $GITHUB_OUTPUT",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "GitHub Actions",
      "name" : "njzjz/wenxian"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.3.1"
      } ]
    } ]
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-77", "CWE-78" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-29T15:39:56Z",
    "nvd_published_at" : "2026-03-31T16:16:33Z"
  }
}