CVE-2026-7768
HIGHCVE-2026-7768 is a high-severity (CVSS 7.5) vulnerability in @fastify/accepts-serializer. O3 Security confirms whether CVE-2026-7768 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
@fastify/accepts-serializer vulnerable to Denial of Service via Unbounded Accept Header Cache Growth
Blast Radius
@fastify/accepts-serializerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
@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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @fastify/accepts-serializer | all versions | 6.0.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @fastify/accepts-serializer. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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 CVE-2026-7768 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-7768 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-7768. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-7768 in your dependencies?
O3 detects CVE-2026-7768 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.