CVE-2026-55831

High

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.

SeverityHigh

CVSS7.5

Exploit probability52. percentile0.7%

ProductNetty

PublishedJul 21, 2026

First seenJul 21, 2026

Weakness typeCWE-770Allocation of resources without limits CWE-400Uncontrolled resource consumption

How to fix

Update

netty netty4.1.136, 4.2.16 or later
io.netty:netty-codec-http4.2.16.Final, 4.1.136.Final or later

Affected products

Product	Affected versions	Fixed in
netty netty	4.1.0 ≤ v < 4.1.136, 4.2.0 ≤ v < 4.2.16	4.1.136, 4.2.16
io.netty:netty-codec-httpMaven	4.2.0.Final ≤ v < 4.2.16.Final, 4.1.0.Final ≤ v < 4.1.136.Final	4.2.16.Final, 4.1.136.Final

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