CVE-2026-42577 Netty: epoll transport denial of service via RST on half-closed TCP connection
Attackers can cause a denial of service via CPU exhaustion in Netty's epoll transport by sending RST packets on half-closed connections.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42577?
CVE-2026-42577 is a high-severity denial of service vulnerability in Netty Netty, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Netty is an asynchronous, event-driven network application framework. From 4.2.0.Final to 4.2.13.Final , 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. This vulnerability is fixed in 4.2.13.Final.
Weakness: CWE-772
Which versions are affected by CVE-2026-42577?
2 open source packages ship an affected version, including io.netty:netty-transport-classes-epoll. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
io.netty:netty-transport-classes-epoll Maven | From 4.2.0.Final | 4.2.13.Final |
io.netty:netty-transport-classes-epoll Maven | From 4.2.0.Final | 4.2.13.Final |
Products include Netty Netty.
How do I fix CVE-2026-42577?
Upgrade io.netty:netty-transport-classes-epoll to 4.2.13.Final or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-42577 being exploited?
There is no known exploitation of CVE-2026-42577 in the wild and no public exploit code.
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- CVE-2026-59901 Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang
- CVE-2026-55851 Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion
- CVE-2026-56745 Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion
Sources
Also known as CLEANSTART-2026-KC30264, CLEANSTART-2026-RE04258, CLEANSTART-2026-RX83323, CLSA-2026-1793142374, DEBIAN-CVE-2026-42577, ECHO-ce1f-ec45-9a4d and 54 more.