GHSA-rwm7-x88c-3g2p is a high-severity (CVSS 7.5) CWE-772 vulnerability in io.netty:netty-transport-classes-epoll. A fix is available for io.netty:netty-transport-classes-epoll — see the affected versions and patch details below.
Netty epoll transport denial of service via RST on half-closed TCP connection
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-rwm7-x88c-3g2p.
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-rwm7-x88c-3g2p 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 377,636 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
io.netty:netty-transport-classes-epollReal-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's epoll transport fails to detect and close TCP connections that receive a RST after being half-closed, leading to stale channels that are never cleaned up and, in some code paths, a 100% CPU busy-loop in the event loop thread.
Affected versions
All versions of 4.2.x netty-transport-classes-epoll up to and including 4.2.12.Final
Fixed in
4.2.13.Final (fix merged into the 4.2 branch via #16689; release not yet cut as of 2026-04-25).
Severity
Medium — Denial of Service (resource exhaustion / CPU spin)
CVSS: 3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - 7.5
CWE: CWE-772: Missing Release of Resource after Effective Lifetime
Description
When a TCP connection using Netty's epoll transport has ALLOW_HALF_CLOSURE enabled (or is in a half-closed state via the HTTP codec), and the remote peer:
- Sends a FIN (half-close), causing the server to mark the input as shutdown, then
- Sends a RST (e.g. by closing with
SO_LINGER=0)
the server-side channel is never closed. This happens because:
epollOutReady()is a no-op when there is no pending flush.epollInReady()short-circuits viashouldBreakEpollInReady()because input is already marked as shutdown.- The
EPOLLERR/EPOLLHUPerror condition is therefore never processed, andchannelInactiveis never fired.
Depending on the Netty version and configuration, this results in:
- Stale channels: The connection is never closed or deregistered. An unauthenticated remote attacker can repeat the sequence to accumulate stale connections, exhausting file descriptors, memory, or connection-count limits.
- CPU busy-loop: In code paths where
clearEpollIn0()is not called during theChannelInputShutdownReadCompleteevent,epoll_waitreturns immediately on every iteration for the affected fd, causing 100% CPU utilization on the event loop thread and starving all other connections multiplexed on it.
Mitigation
- Upgrade to 4.2.13.Final when released (or build from the
4.2branch at commit0ec3d97). - If upgrading is not immediately possible, configure idle timeouts on connections to limit the lifetime of stale channels.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-transport-classes-epoll | ≥ 4.2.0.Final&&< 4.2.13.Final | 4.2.13.Finalio.netty:netty-transport-classes-epoll:4.2.13.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-transport-classes-epoll, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-transport-classes-epoll to 4.2.13.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rwm7-x88c-3g2p 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-rwm7-x88c-3g2p can be triaged on real exposure rather than presence alone.
Tailored to GHSA-rwm7-x88c-3g2p. 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-rwm7-x88c-3g2p in your dependencies?
O3 Security finds GHSA-rwm7-x88c-3g2p across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.