GHSA-455w-c45v-86rg is a high-severity (CVSS 7.5) CWE-754 vulnerability in fastify. EPSS puts its 30-day exploitation probability at 59.2% (99th percentile). A fix is available for fastify — see the affected versions and patch details below.
fastify vulnerable to denial of service via malicious Content-Type
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-455w-c45v-86rg.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-455w-c45v-86rg plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE sits: patch-first territory.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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.
fastifynpmDescription
Impact
An attacker can send an invalid Content-Type header that can cause the application to crash, leading to a possible Denial of Service attack. Only the v4.x line is affected.
(This was updated: upon a close inspection, v3.x is not affected after all).
Patches
Yes, update to > v4.8.0.
Workarounds
You can reject the malicious content types before the body parser enters in action.
const badNames = Object.getOwnPropertyNames({}.__proto__)
fastify.addHook('onRequest', async (req, reply) => {
for (const badName of badNames) {
if (req.headers['content-type'].indexOf(badName) > -1) {
reply.code(415)
throw new Error('Content type not supported')
}
}
})
References
See the HackerOne report #1715536
For more information
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | fastify | ≥ 4.0.0&&< 4.8.1 | 4.8.1npm install fastify@4.8.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fastify, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update fastify to 4.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-455w-c45v-86rg 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-455w-c45v-86rg can be triaged on real exposure rather than presence alone.
Tailored to GHSA-455w-c45v-86rg. 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-455w-c45v-86rg in your dependencies?
O3 Security finds GHSA-455w-c45v-86rg across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.