scimPatch vulnerable to prototype pollution via unfiltered keys in patch

`scim-patch`, a library to perform SCIM patch, prior to version 0.9.1 performs prototype pollution when applying a SCIM PATCH operation whose `value` object contains a key like `"__proto__.someProp"`. After one such patch, `Object.prototype.someProp` is set process-wide, affecting every plain object in the Node process. Any service that calls `scimPatch()` on attacker-controlled JSON (i.e. any SCIM endpoint accepting `PATCH` from an external IdP) is exploitable on a stock Node runtime. Version 0.9.1 contains a patch. A workaround is available. Calling `Object.freeze(Object.prototype)` (and the same on `Array.prototype`, `Function.prototype`) at process startup neutralizes this class of bug — assignment to a frozen prototype becomes a silent no-op in sloppy mode or a `TypeError` in strict mode. Node's `--frozen-intrinsics` flag does this for built-ins automatically.

Source published

7 Aug 2026 21:26:54 UTC

Source modified

10 Aug 2026 14:06:00 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 9.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:L