CVE-2026-42587

Netty: HttpContentDecompressor maxAllocation bypass via Content-Encoding: br/zstd/snappy enables decompression bomb DoS

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.

Affected

netty · io.netty · netty-codec-http · netty-codec-http2

CVSS v3.1 CNA

7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

1.05% chance of exploitation in the next 30 days, 64th percentile

Published

2026-05-13

Updated

2026-09-18

Proof-of-concept exploits (1)

• advisories/GHSA-f6hv-jmp6-3vwv

Security advisories

• netty/netty/security/advisories/GHSA-f6hv-jmp6-3vwv

References

• CVE Record
• NVD entry