CVE-2025-55163 — netty-codec-http2
CVE-2025-55163 is a CWE-770 vulnerability in io.netty:netty-codec-http2. A fix is available for io.netty:netty-codec-http2 — see the affected versions and patch details below.
Netty MadeYouReset HTTP/2 DDoS Vulnerability
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 CVE-2025-55163.
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.
Real-World Exposure
io.netty:netty-codec-http2☕io.netty:netty-codec-http2☕io.grpc:grpc-netty-shadedReal-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
Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.124.Final and 4.2.4.Final, Netty is vulnerable to MadeYouReset DDoS. This is a logical vulnerability in the HTTP/2 protocol, that uses malformed HTTP/2 control frames in order to break the max concurrent streams limit - which results in resource exhaustion and distributed denial of service. This issue has been patched in versions 4.1.124.Final and 4.2.4.Final.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-http2 | ≥ 4.2.0.Alpha1&&< 4.2.4.Final | 4.2.4.Finalio.netty:netty-codec-http2:4.2.4.Final |
| ☕Maven | io.netty:netty-codec-http2 | all versions | 4.1.124.Finalio.netty:netty-codec-http2:4.1.124.Final |
| ☕Maven | io.grpc:grpc-netty-shaded | all versions | 1.75.0io.grpc:grpc-netty-shaded:1.75.0 |
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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-codec-http2 to 4.2.4.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-55163 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 CVE-2025-55163 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-55163. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is rated with an Important severity. It is simple to exploit because it does not require authentication and could result in a denial of service (DoS). While some DoS flaws are classified as Moderate, “MadeYouReset” is Important because of the limited barriers (no specialized tooling or advanced…
| Product | Fixed in | Advisory |
|---|---|---|
| Cryostat 4 on RHEL 9 | cryostat/cryostat-agent-init-rhel9:0.5.2-3 | RHSA-2025:14919 |
| Red Hat build of Apache Camel 4.10.6 for Spring Boot 3.4.9 | netty-codec-http2 | RHSA-2025:14911 |
| Red Hat Build of Apache Camel 4.10 for Quarkus 3.20 | netty-codec-http2 | RHSA-2025:14197 |
| Red Hat build of Quarkus 3.15.6.SP1 | netty-codec-http2 | RHSA-2025:14004 |
| Red Hat build of Quarkus 3.20.2.SP1 | netty-codec-http2 | RHSA-2025:14008 |
| Red Hat Data Grid 8.5.5 | netty-codec-http2 | RHSA-2025:15612 |
| Red Hat JBoss Enterprise Application Platform | io.netty/netty-codec:4.1.127.Final-redhat-00001 | RHSA-2025:17299 |
| Red Hat JBoss Enterprise Application Platform 7.1 EUS for RHEL 7 | eap7-jackson-annotations-0:2.8.11-2.redhat_00004.1.ep7.el7 | RHSA-2026:0742 |
Frequently Asked Questions
Is CVE-2025-55163 in your dependencies?
O3 Security finds CVE-2025-55163 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.