GHSA-q6cq-mhr2-jmr5
Fix: netty/netty@5b68c61GHSA-q6cq-mhr2-jmr5 is a Uncontrolled Resource Consumption vulnerability in io.netty:netty-codec-haproxy. O3 Security confirms whether GHSA-q6cq-mhr2-jmr5 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Netty: [codec-haproxy] Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion
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-q6cq-mhr2-jmr5.
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-haproxy☕io.netty:netty-codec-haproxyReal-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
The HAProxyMessageDecoder in netty's codec-haproxy module performs protocol version detection by reading the 13th byte of the inbound stream as a signed Java byte and widening it to int without masking. When an attacker sends a PROXY protocol v2 binary prefix (0D 0A 0D 0A 00 0D 0A 51 55 49 54 0A) followed by version byte 0xFF, the sign extension produces -1, which collides with the decoder's "need more data" sentinel value. This collision traps the decoder in a version-detection loop where it perpetually requests more data without consuming any bytes, never instantiates the HeaderExtractor that enforces header size limits, and causes ByteToMessageDecoder to accumulate all subsequent inbound bytes into an unbounded cumulation buffer until the JVM exhausts its direct memory allocation.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-haproxy | ≥ 4.2.0.Final&&< 4.2.16.Final | 4.2.16.Final |
| ☕Maven | io.netty:netty-codec-haproxy | ≥ 4.1.0.Final&&< 4.1.136.Final | 4.1.136.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-haproxy. 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-haproxy to 4.2.16.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-q6cq-mhr2-jmr5 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-q6cq-mhr2-jmr5 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-q6cq-mhr2-jmr5. 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 is an Important denial-of-service vulnerability in the Netty `codec-haproxy` module. A remote attacker can send a specially crafted PROXY protocol v2 message, causing unbounded memory accumulation and exhausting direct memory, leading to service unavailability. This impact is significant for applications that…
Frequently Asked Questions
Is GHSA-q6cq-mhr2-jmr5 in your dependencies?
O3 detects GHSA-q6cq-mhr2-jmr5 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.