Vulnerability · Published Jul 21, 2026 · Assigned by GitHub_M

CVE-2026-56816Netty: Memory Exhaustion via HTTP/3 Reserved Frame Types

High 7.5

In plain English

A high-severity uncontrolled resource consumption in netty from netty. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 51% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.6%top 48.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Netty is a network application framework for development of protocol servers and clients. Prior to 4.2.16.Final, Netty's `Http3FrameCodec` buffers incoming data for HTTP/3 reserved frame types up to the wire-specified payload length without limits; `decodeFrame` trusts `payLoadLength`, allowing an attacker to open multiple QUIC streams and send reserved frames with very large payload lengths to cause memory exhaustion and denial of service. This issue is fixed in version 4.2.16.Final.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	netty	no fix listed	DEBIAN-CVE-2026-56816
Debian:13	netty	no fix listed	DEBIAN-CVE-2026-56816
Debian:14	netty	no fix listed	DEBIAN-CVE-2026-56816
Maven	io.netty:netty-codec-http3	4.2.16.Final	GHSA-hpcc-26xq-25fv
Ubuntu:26.10	netty	no fix listed	UBUNTU-CVE-2026-56816

Affected products (as reported)

Vendor	Product	Versions
netty	netty	< 4.2.16.Final

Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/netty/netty/security/advisories/GHSA-hpcc-26xq-25fv x_refsource_CONFIRM
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b x_refsource_MISC
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final x_refsource_MISC