@fastify/accepts-serializer Vulnerable to Denial of Service via Unbounded Accept Header Cache GrowthGHSA-qxhc-wx3p-2wmg
HIGHGHSA-qxhc-wx3p-2wmg is a high-severity (CVSS 7.5) CWE-770 vulnerability in @fastify/accepts-serializer. A fix is available for @fastify/accepts-serializer — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-qxhc-wx3p-2wmg.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@fastify/accepts-serializernpmDescription
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @fastify/accepts-serializer | all versions | 6.0.4npm install @fastify/accepts-serializer@6.0.4 |
Affected Products
fastify\/accepts-serializerfastifyDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @fastify/accepts-serializer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @fastify/accepts-serializer to 6.0.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qxhc-wx3p-2wmg is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is GHSA-qxhc-wx3p-2wmg in your dependencies?
Find it across npm, including transitive dependencies.