CVE-2026-125117Automattic mongoose prototype pollution

What it is

Input can change JavaScript object prototypes, altering behaviour across the application.

How it is reached

An attacker can exploit it over the network, without an account, and nobody has to click anything.

What an attacker gains

A successful attack can take it offline. In practice, this kind of flaw lets an attacker turn crafted data into code execution inside the receiving service.

Is it being exploited?

CISA's SSVC assessment notes a public proof of concept. It can be exploited automatically, at scale.

What to do

1. Upgrade Automattic mongoose to a fixed version for your release line (6.13.12, 7.8.13, 8.24.7).
2. Until it is patched, keep it off the internet or behind a VPN, allowlist or authenticating proxy.

Description from NVD

Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Prior to 6.13.12, 7.8.13, 8.24.7, and 9.11.4, Mongoose can descend into inherited properties while loading database documents in init(), setting dotted paths in $__set, and merging update documents in utils.mergeClone. Attacker-controlled keys such as toString or valueOf can therefore cause Mongoose to write into shared built-in functions instead of an own property. A crafted document, Mixed path, non-strict document or subdocument, findOneAndReplace() replacement, chained update, or Query.prototype.merge() source can overwrite Object.prototype.toString.call, causing later queries on unrelated models to fail until the process restarts. Separately, when an attacker controls the dotted path passed to doc.set(path, value) for a subdocument configured with strict: false, descent through $__set can reach $__schema and alter shared validators or schema options for later documents. Mongoose already blocks __proto__, constructor, and prototype, so this issue overwrites properties on reachable shared objects rather than adding new properties directly to Object.prototype. This issue is fixed in versions 6.13.12, 7.8.13, 8.24.7, and 9.11.4.