{"id":"GHSA-gg2g-m5wc-vccq","summary":"Rebuild-bot workflow may allow unauthorised repository modifications","details":"### Impact\n\n`projen` is a project generation tool that synthesizes project configuration files such as `package.json`, `tsconfig.json`, `.gitignore`, GitHub Workflows, `eslint`, `jest`, and more, from a well-typed definition written in JavaScript. Users of projen's `NodeProject` project type (including any project type derived from it) include a `.github/workflows/rebuild-bot.yml` workflow that may allow any GitHub user to trigger execution of un-trusted code in the context of the \"main\" repository (as opposed to that of a fork). In some situations, such untrusted code may potentially be able to commit to the \"main\" repository.\n\nThe rebuild-bot workflow is triggered by comments including `@projen rebuild` on pull-request to trigger a re-build of the projen project, and updating the pull request with the updated files. This workflow is triggered by an `issue_comment` event, and thus always executes with a `GITHUB_TOKEN` belonging to the repository into which the pull-request is made (this is in contrast with workflows triggered by `pull_request` events, which always execute with a `GITHUB_TOKEN` belonging to the repository from which the pull-request is made).\n\nRepositories that do not have branch protection configured on their default branch (typically `main` or `master`) could possibly allow an untrusted user to gain access to secrets configured on the repository (such as NPM tokens, etc). Branch protection prohibits this escalation, as the managed `GITHUB_TOKEN` would not be able to modify the contents of a protected branch and affected workflows must be defined on the default branch. \n\n### Patches\n\nThe issue was mitigated in version `0.16.41` of the `projen` tool, which removes the `issue_comment` trigger from this workflow. Version `0.17.0` of projen completely removes the `rebuild-bot.yml` workflow.\n\n### Workarounds\n\nThe recommended way to address the vulnerability is to upgrade `projen`. Users who cannot upgrade `projen` may also remove the `.github/workflows/rebuild-bot.yml` file and add it to their `.gitignore` file (via `projenrc.js`) to mitigate the issue.\n\n### References\n\nThe `rebuild-bot.yml` workflow managed by `projen` is only one occurrence of a GitHub Workflows mis-configuration, but it may also be present in other workflows not managed by `projen` (either hand-written, or managed by other tools). For more information on this class of issues, the [Keeping your GitHub Actions and workflows secure: Preventing pwn requests][1] article provides a great overview of the problem.\n \n\n[1]: https://securitylab.github.com/research/github-actions-preventing-pwn-requests","aliases":["CVE-2021-21423","PYSEC-2021-111"],"modified":"2026-07-08T06:27:36.747299841Z","published":"2021-04-06T18:36:40Z","database_specific":{"nvd_published_at":"2021-04-06T19:15:00Z","cwe_ids":["CWE-527"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2021-04-06T18:36:19Z"},"references":[{"type":"WEB","url":"https://github.com/projen/projen/security/advisories/GHSA-gg2g-m5wc-vccq"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21423"},{"type":"WEB","url":"https://github.com/projen/projen/commit/36030c6a4b1acd0054673322612e7c70e9446643"},{"type":"PACKAGE","url":"https://github.com/projen/projen"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/projen/PYSEC-2021-111.yaml"},{"type":"WEB","url":"https://www.npmjs.com/package/projen"}],"affected":[{"package":{"name":"projen","ecosystem":"npm","purl":"pkg:npm/projen"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.6.0"},{"fixed":"0.16.41"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/04/GHSA-gg2g-m5wc-vccq/GHSA-gg2g-m5wc-vccq.json"}},{"package":{"name":"projen","ecosystem":"PyPI","purl":"pkg:pypi/projen"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.16.41"}]}],"versions":["0.14.0","0.14.1","0.14.10","0.14.2","0.14.3","0.14.4","0.14.5","0.14.6","0.14.7","0.14.8","0.14.9","0.15.0","0.15.1","0.15.10","0.15.11","0.15.12","0.15.13","0.15.14","0.15.15","0.15.16","0.15.17","0.15.18","0.15.2","0.15.3","0.15.4","0.15.5","0.15.6","0.15.7","0.15.8","0.15.9","0.16.0","0.16.1","0.16.10","0.16.11","0.16.12","0.16.13","0.16.14","0.16.15","0.16.16","0.16.17","0.16.18","0.16.19","0.16.2","0.16.20","0.16.21","0.16.22","0.16.23","0.16.24","0.16.25","0.16.26","0.16.27","0.16.28","0.16.29","0.16.3","0.16.30","0.16.31","0.16.32","0.16.33","0.16.34","0.16.35","0.16.36","0.16.37","0.16.38","0.16.39","0.16.4","0.16.40","0.16.5","0.16.7","0.16.8","0.16.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/04/GHSA-gg2g-m5wc-vccq/GHSA-gg2g-m5wc-vccq.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"}]}