CVE-2021-21423

What it is

`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. The 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). Repositories 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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering.

Exploit odds

1.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-04-06 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:35 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.4% in the next 30 days (EPSS).
• Severity: 6.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-04-06 19:15 UTC

Last modified

2026-06-17 03:35 UTC

Exploit probability

1.4% · EPSS, next 30 days

Weakness

CWE-527

Record status

Modified

Affected

• Projen Project Projen < 0.16.41

Attack profile CVSS 3.1 · 6.8

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-21423.md and follow it. Check whether this project is affected by CVE-2021-21423. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge