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Vulnerability · Published May 13, 2026 · Assigned by GitHub_M

CVE-2026-42587Netty: HttpContentDecompressor maxAllocation bypass via Content-Encoding: br/zstd/snappy enables decompression bomb DoS

High 7.5

In plain English

A high-severity uncontrolled resource consumption in netty-codec-http from io.netty. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 63% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)1.0%top 37.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12nettyno fix listedDEBIAN-CVE-2026-42587
Debian:13nettyno fix listedDEBIAN-CVE-2026-42587
Debian:14nettyno fix listedDEBIAN-CVE-2026-42587
Mavenio.netty:netty-codec-http4.2.13.FinalGHSA-f6hv-jmp6-3vwv
Mavenio.netty:netty-codec-http4.1.133.FinalGHSA-f6hv-jmp6-3vwv
Mavenio.netty:netty-codec-http24.1.133.FinalGHSA-f6hv-jmp6-3vwv
Mavenio.netty:netty-codec-http24.2.13.FinalGHSA-f6hv-jmp6-3vwv
Ubuntu:25.10nettyno fix listedUBUNTU-CVE-2026-42587

Affected products (as reported)

VendorProductVersions
netty netty >= 4.2.0.Alpha1, < 4.2.13.Final< 4.1.133.Final
io.netty netty-codec-http >= 4.2.0.Alpha1, < 4.2.13.Final< 4.1.133.Final
io.netty netty-codec-http2 >= 4.2.0.Alpha1, < 4.2.13.Final< 4.1.133.Final

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

References