GHSA-rv63-4mwf-qqc2
MEDIUMGHSA-rv63-4mwf-qqc2 is a medium-severity (CVSS 6.5) CWE-345 vulnerability in hono. O3 Security confirms whether GHSA-rv63-4mwf-qqc2 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
hono: Body Limit Middleware can be bypassed on AWS Lambda by understating `Content-Length`
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-rv63-4mwf-qqc2.
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-rv63-4mwf-qqc2 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 0 CVEs with a current EPSS score, this one falls in the < 10% 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.
hononpmDescription
Summary
The Body Limit Middleware trusts the request's Content-Length header to decide whether a body is within the limit. On AWS Lambda (API Gateway v1/v2, ALB, VPC Lattice, and Lambda@Edge) the body is delivered fully buffered and the adapter builds the request with the client-declared Content-Length, which need not match the actual payload. A client can declare a tiny Content-Length while sending a much larger body, slipping past the limit.
Details
When Content-Length is present and Transfer-Encoding is absent, the middleware compares the declared value against the limit and passes the request through if it is small enough. On standards-based runtimes the transport enforces that Content-Length matches the body, so this is safe. The Lambda adapters instead reconstruct the request from a buffered payload and copy the client's Content-Length verbatim, so the declared length and the real body size are decoupled.
This issue affects applications deployed on AWS Lambda that rely on the Body Limit Middleware to cap request body size.
Impact
The declared body-size limit can be bypassed: a handler reads a payload larger than the configured maximum. Processing the oversized payload (large JSON, multipart, etc.) consumes additional CPU and memory per request. The payload remains bounded by the platform's request size limits, and Lambda isolates invocations, so the impact is increased per-request resource usage rather than full denial of service. This affects applications deployed on AWS Lambda that use the Body Limit Middleware.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | hono | all versions | 4.12.25 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono. 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 hono to 4.12.25 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rv63-4mwf-qqc2 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-rv63-4mwf-qqc2 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-rv63-4mwf-qqc2. 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-rv63-4mwf-qqc2 in your dependencies?
O3 detects GHSA-rv63-4mwf-qqc2 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.