CVE-2023-52137: Tj actions/verify changed files Potential Actions Command Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-ghm2-rq8q-wrhc",
  "modified" : "2024-01-02T16:42:27Z",
  "published" : "2024-01-02T16:42:27Z",
  "aliases" : [ "CVE-2023-52137" ],
  "summary" : "Potential Actions command injection in output filenames (GHSL-2023-275)",
  "details" : "### Summary\nThe [`tj-actions/verify-changed-files`](https://github.com/tj-actions/verify-changed-files) action allows for command injection in changed filenames, allowing an attacker to execute arbitrary code and potentially leak secrets.\n\n### Details\nThe [`verify-changed-files`](https://github.com/tj-actions/verify-changed-files) workflow returns the list of files changed within a workflow execution.\n\nThis could potentially allow filenames that contain special characters such as `;` and \\` (backtick) which can be used by an attacker to take over the [GitHub Runner](https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners) if the output value is used in a raw fashion (thus being directly replaced before execution) inside a `run` block. By running custom commands an attacker may be able to steal **secrets** such as `GITHUB_TOKEN` if triggered on other events than `pull_request`. For example on `push`.\n\n#### Proof of Concept\n\n1. Submit a pull request to the repository with a new file injecting a command. For example `$(whoami).txt` would be a valid filename.\n2. Upon approval of the workflow (triggered by the pull request), the action will get executed and the malicious pull request filename will flow into the `List all changed files tracked and untracked files` step.\n\n```yaml\n- name: List all changed files tracked and untracked files\n  run: |\n    echo \"Changed files: ${{ steps.verify-changed-files.outputs.changed_files }}\"\n```\n\nExample output:\n\n```yaml\n##[group]Run echo \"Changed files: $(whoami).txt\"\n  echo \"Changed files: $(whoami).txt\"\u001B[0m\nshell: /usr/bin/bash -e {0}\n##[endgroup]\nChanged files: runner.txt\n```\n\n### Impact\nThis issue may lead to arbitrary command execution in the GitHub Runner.\n\n### Resolution\n- A new `safe_output` input would be enabled by default and return filename paths escaping special characters like ;, ` (backtick), $, (), etc for bash environments.\n\n- A safe recommendation of using environment variables to store unsafe outputs.\n\n```yaml\n- name: List all changed files tracked and untracked files\n  env:\n     CHANGED_FILES: ${{ steps.verify-changed-files.outputs.changed_files }}\n  run: |\n    echo \"Changed files: $CHANGED_FILES\"\n```\n\n\n### Resources\n\n* [Keeping your GitHub Actions and workflows secure Part 2: Untrusted input](https://securitylab.github.com/research/github-actions-untrusted-input/)\n* [Keeping your GitHub Actions and workflows secure Part 1: Preventing pwn requests](https://securitylab.github.com/research/github-actions-preventing-pwn-requests/)\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "GitHub Actions",
      "name" : "tj-actions/verify-changed-files"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "17"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/tj-actions/verify-changed-files/security/advisories/GHSA-ghm2-rq8q-wrhc"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-52137"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tj-actions/verify-changed-files/commit/498d3f316f501aa72485060e8c96fde7b2014f12"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tj-actions/verify-changed-files/commit/592e305da041c09a009afa4a43c97d889bed65c3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/tj-actions/verify-changed-files"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-77" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-01-02T16:42:27Z",
    "nvd_published_at" : "2023-12-29T17:16:07Z"
  }
}