Vulnerability · Published Jul 21, 2026 · Assigned by GitHub_M

CVE-2026-56819Netty: HTTP/2 decompression leaks ByteBuf reference count when the decompressor channel is already closed (Direct memory leak / OOM DoS)

High 7.5

In plain English

A high-severity uncontrolled resource consumption in netty from netty. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.7%top 48.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack tooling1Public PoC

Official description

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final, a remote unauthenticated peer can leak one direct `ByteBuf` per HTTP/2 `DATA` frame in applications that enable HTTP/2 content decompression via `DelegatingDecompressorFrameListener`. When a `DATA` frame is processed for a stream whose decompressor has already been closed, `Http2Decompressor.decompress(...)` calls `decompressor.writeInbound(data.retain())` and does not release the retained buffer on the error path, eventually exhausting direct memory and crashing the JVM. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	netty	no fix listed	DEBIAN-CVE-2026-56819
Debian:13	netty	no fix listed	DEBIAN-CVE-2026-56819
Debian:14	netty	no fix listed	DEBIAN-CVE-2026-56819
Maven	io.netty:netty-codec-http2	4.2.16.Final	GHSA-93wv-jw9v-4972
Maven	io.netty:netty-codec-http2	4.1.136.Final	GHSA-93wv-jw9v-4972
Ubuntu:26.10	netty	no fix listed	UBUNTU-CVE-2026-56819

Affected products (as reported)

Vendor	Product	Versions
netty	netty	>= 4.2.0.Final, < 4.2.16.Final>= 4.1.0.Final, < 4.1.136.Final

Weakness: CWE-400, CWE-401 · 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-93wv-jw9v-4972 x_refsource_CONFIRM
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b x_refsource_MISC
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6 x_refsource_MISC
https://github.com/netty/netty/releases/tag/netty-4.1.136.Final x_refsource_MISC
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final x_refsource_MISC