CVE-2026-7768: Fastify Fastify/accepts-Serializer

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

@fastify/accepts-serializer cached serializer-selection results keyed by the request Accept header without a size limit or eviction policy. A remote unauthenticated client could send many distinct but matching Accept header variants to make the cache grow unbounded, eventually exhausting the Node.js heap and crashing the process. Versions <= 6.0.3 are affected. Update to 6.0.4 or later, which bounds the cache via an LRU with a default size of 100 entries, configurable through the new cacheSize plugin option.

Affected products

• Fastify Fastify/accepts-Serializer: before 6.0.4 (fixed in 6.0.4)

Published 2026-05-04. Last modified 2026-06-17.