CVE-2021-21423: Projen Rebuild-bot Workflow May Allow Unauthorised Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gg2g-m5wc-vccq",
  "modified" : "2024-10-21T20:05:47Z",
  "published" : "2021-04-06T18:36:40Z",
  "aliases" : [ "CVE-2021-21423" ],
  "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",
  "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "projen"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.6.0"
      }, {
        "fixed" : "0.16.41"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "projen"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.16.41"
      } ]
    } ]
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-527" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-04-06T18:36:19Z",
    "nvd_published_at" : "2021-04-06T19:15:00Z"
  }
}