GHSA-mrq3-vjjr-p77c is a low-severity (CVSS 3.7) CWE-770 vulnerability in fastify. O3 Security confirms whether GHSA-mrq3-vjjr-p77c is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Fastify Vulnerable to DoS via Unbounded Memory Allocation in sendWebStream
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
fastifynpmDescription
Impact
A Denial of Service vulnerability in Fastify’s Web Streams response handling can allow a remote client to exhaust server memory. Applications that return a ReadableStream (or Response with a Web Stream body) via reply.send() are impacted. A slow or non-reading client can trigger unbounded buffering when backpressure is ignored, leading to process crashes or severe degradation.
Patches
The issue is fixed in Fastify 5.7.3. Users should upgrade to 5.7.3 or later.
Workarounds
Avoid sending Web Streams from Fastify responses (e.g., ReadableStream or Response bodies). Use Node.js streams (stream.Readable) or buffered payloads instead until the project can upgrade.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | fastify | all versions | 5.7.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fastify. 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 to 5.7.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mrq3-vjjr-p77c 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 GHSA-mrq3-vjjr-p77c 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 GHSA-mrq3-vjjr-p77c. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-mrq3-vjjr-p77c in your dependencies?
O3 detects GHSA-mrq3-vjjr-p77c across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.