Nx: OS command injection via git revisions and remote refs

Why it is Yellow

• CVSS 8.5 high
• On your watchlist: npm

Affected packages

References

• https://github.com/advisories/GHSA-w2vw-w76x-qr89
• https://github.com/nrwl/nx/security/advisories/GHSA-w2vw-w76x-qr89
• https://github.com/nrwl/nx/pull/36348
• https://github.com/nrwl/nx/pull/36379
• https://github.com/nrwl/nx/commit/11ab38573478172109bb5306cb30ca4af246caf0
• https://github.com/nrwl/nx/commit/4159295a037fdbd8e7f44a33a19d85ab3792415b
• https://github.com/nrwl/nx/commit/9ce184a04d2098a4797c8b0d6877ee079b751abf
• https://github.com/nrwl/nx/commit/c12850ce7b364db08e325c13541641d754db7123
• https://github.com/nrwl/nx/commit/cd9b3c068e17adc9c1722b35b9ca962b98542c20
• https://github.com/nrwl/nx/commit/cf996496bbad727362d48292b50fafc8c3665847

Original description

## Summary Nx core builds several `git` invocations as shell command strings with untrusted values interpolated into them, so a value that should be a git revision or ref is parsed by `/bin/sh` instead. Two entry points are reachable by an attacker: `affected` commands, where `defaultBase` / `affected.defaultBase` from `nx.json` (and the `NX_BASE` / `NX_HEAD` environment variables) reach `git merge-base` and `git diff`; and `nx import`, where a branch name advertised by a remote repository reaches `git fetch`, `git checkout`, and `git config`. In both cases an attacker who controls a repository — or who opens a pull request against one — gets arbitrary command execution on the machine of anyone who runs an ordinary Nx command against it, including CI runners. The `affected` path is the more serious of the two. `nx affected` and `nx show projects --affected` run constantly in CI, so a pull request that changes nothing but `nx.json` is enough to execute code on the runner with whatever credentials that job holds. ## Severity Exploitable by anyone who controls repository content — a fork's pull request, or a repository the victim clones — that the victim then runs an ordinary `nx affected` or `nx import` against; no access to the victim's machine is required. We have no evidence of exploitation in the wild. ## Affected & Patched Versions | Package | Vulnerable | Patched | | --- | --- | --- | | `nx` | `>= 14.0.0, < 22.7.8`; `>= 23.0.0, < 23.1.1` | `22.7.8`, `23.1.1` | Treat every version below the patched ones as affected. ## Remediation Upgrade to **22.7.8** (22.x line) or **23.1.1** (23.x line) or later: ``` nx migrate 23.1.1 ``` The fix is a drop-in — no configuration changes are required. If you cannot upgrade, treat `nx.json` from untrusted sources as executable content, do not run `affected` commands against pull requests you have not reviewed, and do not run `nx import` against repositories you do not trust. ## Details ### `affected` commands Nx computes the merge base and the changed-file set by building `git merge-base` and `git diff` command lines as strings and running them through a shell. The base and head revisions in those strings come from `nx.json`'s `defaultBase` / `affected.defaultBase` or from the `NX_BASE` / `NX_HEAD` environment variables, and a related code path reads file contents with `git show <revision>:<path>` the same way. Because a shell parses the whole line, a revision value containing shell syntax is executed rather than passed to `git`. The revisions are wrapped in double quotes, which looks protective but is not: POSIX shells still perform command substitution inside double quotes, so a value of `$(…)` runs without needing to break out of the quotes. ### `nx import` The `GitRepository` helper runs every git operation — `fetch`, `checkout`, `reset`, `config`, and others — by interpolating its arguments into a shell command string. The untrusted argument is a branch name: `nx import` lists the branches a remote advertises, offers them to the user to choose from, and feeds the chosen name back into those commands. A hostile repository controls the names of its own branches, so it controls the command that runs when one is selected. ## Credits - **Arkadiusz Marta** (RE:SOURCE) — Reporter