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CVE-2026-42587

High

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpContentDecompressor accepts a maxAllocation parameter to limit decompression buffer size and prevent decompression bomb attacks. This limit is correctly enforced for gzip and deflate encodings via ZlibDecoder, but is silently ignored when the content encoding is br (Brotli), zstd, or snappy. An attacker can bypass the configured decompression limit by sending a compressed payload with Content-Encoding: br instead of Content-Encoding: gzip, causing unbounded memory allocation and out-of-memory denial of service. The same vulnerability exists in DelegatingDecompressorFrameListener for HTTP/2 connections. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

SeverityHigh
CVSS7.5
Exploit probability—
ProductNetty
PublishedMay 13, 2026
First seenMay 13, 2026
Weakness typeCWE-400Uncontrolled resource consumption

How to fix

Update
  • netty netty4.1.133, 4.2.13 or later
  • io.netty:netty-codec-http4.2.13.Final, 4.1.133.Final or later
  • io.netty:netty-codec-http24.2.13.Final, 4.1.133.Final or later
Vendor advisories

Affected products

ProductAffected versionsFixed in
netty nettyv < 4.1.133, 4.2.0 ≤ v < 4.2.134.1.133, 4.2.13
io.netty:netty-codec-httpMaven4.2.0.Alpha1 ≤ v < 4.2.13.Final, v < 4.1.133.Final4.2.13.Final, 4.1.133.Final
io.netty:netty-codec-http2Maven4.2.0.Alpha1 ≤ v < 4.2.13.Final, v < 4.1.133.Final4.2.13.Final, 4.1.133.Final

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