React Native Worklets EUVD-2026-86500

Exploitation requires that the React Native application actually route attacker-controlled data (e.g., a JSON object with a nested __proto__ property) through the affected Worklets serialization path (clonePlainJSObject / SerializableObject in react-native-worklets before 0.12.2). The app must use react-native-worklets/Reanimated and deserialize externally supplied data via worklets; apps that never pass untrusted input through this path are not exploitable. Limiting factors: impact is availability-only (a crash, not code execution or data disclosure); the CVSS 4.0 UI:P indicates some passive user interaction (the malformed data must be processed/rendered) is needed; and the DoS only becomes persistent if the attacker data is stored by the application.

This is a genuine but low-to-moderate priority issue. The CVSS 4.0 vector (AV:N/AC:L/PR:N/UI:P) describes a network-reachable, unauthenticated, low-complexity flaw, but the impact is deliberately narrow: only VA:L (availability, low) with VC:N/VI:N - no confidentiality or integrity loss. Despite the alarming 'prototype pollution' (CWE-1321) label, which often implies RCE or auth bypass, the vendor and the fix confirm the realistic outcome is a crash / denial of service, not code execution - the pollution corrupts an object created during serialization and causes React Native Worklets to throw when the malformed object is later processed. No EPSS score, no CISA KEV listing, and no public exploit code were provided, so this is not confirmed to be actively exploited. The one aggravating factor is persistence: if attacker-controlled data is stored, the DoS can recur across app restarts (reflected in the 4.0 V:D 'diffuse'/RE:L recovery metrics). The 5.3 score is proportionate and arguably generous for an availability-only mobile-app crash. Net: fix on a normal patch cadence; not an emergency.

An attacker submits a JSON payload containing a nested __proto__ key into a React Native app that passes user-controlled data through the Worklets serialization path (clonePlainJSObject / SerializableObject). When the app subsequently processes the malformed serialized object on the UI/worklet runtime, it crashes. No public exploit code was identified, but the triggering condition is simple and documented in public issue #10436.