@fastify/accepts-serializer Vulnerable to Denial of Service via Unbounded Accept Header Cache Growth
Impact
@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. Under sustained load, this can exhaust the Node.js heap and crash the process.
Patches
Update to @fastify/accepts-serializer >= 6.0.4. The cache is now bounded by an LRU with a default size of 100 entries, configurable via the new cacheSize plugin option.
Workarounds
None. Upgrade is required.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @fastify/accepts-serializer | < 6.0.4 | 6.0.4 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-770- Platform
- npm
- Package
@fastify/accepts-serializer- Disclosed
- 08.05.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-qxhc-wx3p-2wmg - CC BY 4.0
Vulnerability history: @fastify/accepts-serializer
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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