CVE-2026-120819: Use-after-free in Wasm JS-BSON bridge lets read-only users read 24 KiB via $accumulator

A memory-management flaw in the server-side JavaScript execution component of MongoDB Server can allow an authenticated user holding only read privileges to cause the server to access memory that has already been released. By submitting a specially crafted database command that runs user-supplied JavaScript, the user can cause a bounded amount of adjacent process memory to be returned in the command's result. This results in the user obtaining information they are not authorized to access. Integrity and availability are not affected.