CVE-2023-51664: Tj actions/changed files Tj-actions/changed-files Has Potential Actions Command Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mcph-m25j-8j63",
  "modified" : "2024-01-02T16:41:27Z",
  "published" : "2024-01-02T16:41:27Z",
  "aliases" : [ "CVE-2023-51664" ],
  "summary" : "tj-actions/changed-files has Potential Actions command injection in output filenames (GHSL-2023-271)",
  "details" : "### Summary\nThe `tj-actions/changed-files` workflow allows for command injection in changed filenames, allowing an attacker to execute arbitrary code and potentially leak secrets.\n\n### Details\nThe [`changed-files`](https://github.com/tj-actions/changed-files) action returns a list of files changed in a commit or pull request which provides an `escape_json` input [enabled by default](https://github.com/tj-actions/changed-files/blob/94549999469dbfa032becf298d95c87a14c34394/action.yml#L136), only escapes `\"` for JSON values. \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 a repository with a new file injecting a command. For example `$(whoami).txt` which is 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` step below.\n\n```yaml\n      - name: List all changed files\n        run: |\n          for file in ${{ steps.changed-files.outputs.all_changed_files }}; do\n            echo \"$file was changed\"\n          done\n```\n\nExample output:\n\n```yaml\n##[group]Run for file in $(whoami).txt; do\n    for file in $(whoami).txt; do\n        echo \"$file was changed\"\n    done\nshell: /usr/bin/bash -e {0}\n##[endgroup]\nrunner.txt was changed\n```\n\n### Impact\n\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\n  env:\n    ALL_CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files }}\n  run: |\n    for file in \"$ALL_CHANGED_FILES\"; do\n      echo \"$file was changed\"\n    done\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/)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "GitHub Actions",
      "name" : "tj-actions/changed-files"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "41"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/tj-actions/changed-files/security/advisories/GHSA-mcph-m25j-8j63"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-51664"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tj-actions/changed-files/commit/0102c07446a3cad972f4afcbd0ee4dbc4b6d2d1b"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tj-actions/changed-files/commit/716b1e13042866565e00e85fd4ec490e186c4a2f"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tj-actions/changed-files/commit/ff2f6e6b91913a7be42be1b5917330fe442f2ede"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/tj-actions/changed-files"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-74", "CWE-77" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-01-02T16:41:27Z",
    "nvd_published_at" : "2023-12-27T17:15:08Z"
  }
}