GHSA-563q-j3cm-6jxm
MEDIUMGHSA-563q-j3cm-6jxm is a medium-severity (CVSS 5.3) CWE-770 vulnerability in io.netty:netty-codec-http2. O3 Security confirms whether GHSA-563q-j3cm-6jxm is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Netty susceptible to HTTP/2 Reset Attack with different on-the-wire signature
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.
Blast Radius
io.netty:netty-codec-http2☕io.netty:netty-codec-http2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Netty HTTP/2 max header size handling produces attack similar to HTTP/2 Rapid Reset.
Details
There is a setting in the http2 specification called SETTINGS_MAX_HEADER_LIST_SIZE. According to the RFC: “This advisory setting informs a peer of the maximum field section size that the sender is prepared to accept, in units of octets.”
When a client sends that setting to Netty, it appears that Netty will behave as follows:
- Read the request
- Proxy the request to the origin
- Attempt to produce a response
- Create an exception while writing the headers for the response
Functionally, this should be similar to the http2 reset attack, but with a different on-the-wire signature.
Remediation
When speaking with clients, Netty should potentially treat this as “advisory” and ignore it. It would be best to ignore the SETTINGS_MAX_HEADER_LIST_SIZE setting from clients (or ignore it when sending to clients). According to the spec, a server does not need to honor this advisory setting, and it appears that other http/2 implementations ignore it when acting as a server.
Impact
This is a DDoS attack similar to the HTTP/2 Rapid Reset Attack.
Credit
Jonathan Looney (Engineering, Netflix)
Contact
Ashley Tolbert (Security, Netflix) - [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-http2 | ≥ 4.2.0.Final&&< 4.2.15.Final | 4.2.15.Final |
| ☕Maven | io.netty:netty-codec-http2 | all versions | 4.1.135.Final |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-http2. 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 io.netty:netty-codec-http2 to 4.2.15.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-563q-j3cm-6jxm 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-563q-j3cm-6jxm 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-563q-j3cm-6jxm. 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-563q-j3cm-6jxm in your dependencies?
O3 detects GHSA-563q-j3cm-6jxm across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.