CVE-2023-25576
HIGHCVE-2023-25576 is a high-severity (CVSS 7.5) CWE-770 vulnerability in @fastify/multipart. O3 Security confirms whether CVE-2023-25576 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
@fastify/multipart vulnerable to DoS due to unlimited number of parts
Blast Radius
@fastify/multipart📦@fastify/multipartReal-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/multipart is a Fastify plugin to parse the multipart content-type. Prior to versions 7.4.1 and 6.0.1, @fastify/multipart may experience denial of service due to a number of situations in which an unlimited number of parts are accepted. This includes the multipart body parser accepting an unlimited number of file parts, the multipart body parser accepting an unlimited number of field parts, and the multipart body parser accepting an unlimited number of empty parts as field parts. This is fixed in v7.4.1 (for Fastify v4.x) and v6.0.1 (for Fastify v3.x). There are no known workarounds.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @fastify/multipart | all versions | 6.0.1 |
| 📦npm | @fastify/multipart | ≥ 7.0.0&&< 7.4.1 | 7.4.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @fastify/multipart. 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/multipart to 6.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-25576 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-2023-25576 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-2023-25576. 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-2023-25576 in your dependencies?
O3 detects CVE-2023-25576 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.