Netty up to 4.1.134/4.2.14 SpdyHttpDecoder memory allocation

Summaryinfo

A vulnerability was found in Netty up to 4.1.134/4.2.14. It has been rated as problematic. This issue affects some unknown processing of the component SpdyHttpDecoder. Performing a manipulation results in memory allocation. This vulnerability is reported as CVE-2026-56745. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Netty up to 4.1.134/4.2.14. This affects an unknown function of the component SpdyHttpDecoder. The manipulation with an unknown input leads to a memory allocation vulnerability. CWE is classifying the issue as CWE-789. The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated. This is going to have an impact on availability. The summary by CVE is:

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final, the `SpdyHttpDecoder` handler in Netty's SPDY-to-HTTP codec allocates a pooled `ByteBuf` when processing a client-initiated `SYN_STREAM` frame with `FLAG_FIN=0` and stores the partially constructed `FullHttpRequest` in `messageMap`; when the remote peer sends `RST_STREAM` for that stream or the accumulated content exceeds `maxContentLength`, the decoder removes the entry but does not release the pooled `ByteBuf`, causing native memory exhaustion. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-56745 since 06/22/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available.

Upgrading to version 4.1.136.Final or 4.2.16.Final eliminates this vulnerability.

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Productinfo

Name

• Netty

Version

• 4.1.134
• 4.2.0
• 4.2.1
• 4.2.2
• 4.2.3
• 4.2.4
• 4.2.5
• 4.2.6
• 4.2.7
• 4.2.8
• 4.2.9
• 4.2.10
• 4.2.11
• 4.2.12
• 4.2.13
• 4.2.14

Website

• Product: https://github.com/netty/netty/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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