CVE-2026-53609 Apostrophe has Server-Side Prototype Pollution in apos.util.set via patch operators that leads to process-wide authorization bypass
An authenticated editor can pollute the prototype to bypass authorization checks on all piece-type REST API endpoints for subsequent unauthenticated requests.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53609?
CVE-2026-53609 is a critical authentication bypass vulnerability in apostrophecms apostrophe, published on 12 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
ApostropheCMS is an open-source Node.js content management system. In versions up to and including 4.30.0, `apos.util.set()` traverses dot-notation paths without sanitizing `__proto__`, allowing an authenticated editor to write arbitrary values to `Object.prototype` via the `$pullAll` patch operator. A confirmed gadget in `publicApiCheck()` causes this to bypass authorization on all piece-type REST API endpoints for every subsequent unauthenticated request, for the lifetime of the Node.js process. As of time of publication, no known patched versions are available.
Weakness: CWE-1321
Which versions are affected by CVE-2026-53609?
2 open source packages ship an affected version, including apostrophe.
| Package | Affected | Fixed in |
|---|---|---|
apostrophe npm | All versions | 4.31.0 |
apostrophe npm | All versions | 4.31.0 |
How do I fix CVE-2026-53609?
Upgrade apostrophe to 4.31.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-53609 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53609 exists.
Sources
Also known as GHSA-6h5j-32cf-4253.