Log in Start free

Vulnerability · Published Jul 20, 2026 · Assigned by GitHub_M

CVE-2026-55831Netty SPDY SETTINGS frame count materializes unbounded settings map

High 7.5

In plain English

A high-severity resource allocation without limits 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). 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 toolingNoneno public tooling known

Official description

Netty is a network application framework for development of protocol servers and clients. Prior to 4.1.136.Final and 4.2.16.Final, Netty's SPDY SETTINGS decoder accepts a peer-declared SETTINGS entry count up to the 24-bit frame-length limit and materializes every unique setting ID in `DefaultSpdySettingsFrame`, allowing a remote SPDY/3.1 peer to send a syntactically valid roughly 2 MiB SETTINGS frame that creates 262144 map entries and amplifies network input into heap growth and ordered-map insertion work. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12nettyno fix listedDEBIAN-CVE-2026-55831
Debian:13nettyno fix listedDEBIAN-CVE-2026-55831
Debian:14nettyno fix listedDEBIAN-CVE-2026-55831
Mavenio.netty:netty-codec-http4.2.16.FinalGHSA-6jqx-86gh-f27w
Mavenio.netty:netty-codec-http4.1.136.FinalGHSA-6jqx-86gh-f27w
Ubuntu:26.10nettyno fix listedUBUNTU-CVE-2026-55831

Affected products (as reported)

VendorProductVersions
netty netty >= 4.2.0.Final, < 4.2.16.Final>= 4.1.0.Final, < 4.1.136.Final

Weakness: CWE-770, CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References