{"id":"GHSA-ghm2-rq8q-wrhc","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","aliases":["CVE-2023-52137"],"modified":"2024-01-02T16:42:27Z","published":"2024-01-02T16:42:27Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2024-01-02T16:42:27Z","nvd_published_at":"2023-12-29T17:16:07Z","cwe_ids":["CWE-20","CWE-77"],"severity":"HIGH"},"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"}],"affected":[{"package":{"name":"tj-actions/verify-changed-files","ecosystem":"GitHub Actions"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"17"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2024/01/GHSA-ghm2-rq8q-wrhc/GHSA-ghm2-rq8q-wrhc.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:L"}]}