Netty up to 4.1.135.Final/4.2.15.Final readableBytes allocation of resources

Summaryinfo

A vulnerability, which was classified as problematic, was found in Netty up to 4.1.135.Final/4.2.15.Final. The affected element is the function readableBytes. The manipulation results in allocation of resources. This vulnerability is identified as CVE-2026-46340. The attack can be executed remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Netty up to 4.1.135.Final/4.2.15.Final. Affected is the function readableBytes. The manipulation with an unknown input leads to a allocation of resources vulnerability. CWE is classifying the issue as CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. This is going to have an impact on availability. CVE summarizes:

Netty is a network application framework for development of protocol servers and clients. In versions of netty-transport-sctp prior to 4.1.135.Final and 4.2.15.Final, for each non-complete SctpMessage fragment the handler does `fragments.put(streamId, Unpooled.wrappedBuffer(frag, byteBuf))`, wrapping the previous accumulator and the new slice into a *new* CompositeByteBuf every time. After N fragments the accumulator is an N-deep chain of composites, each holding references and component arrays; readableBytes()/getBytes() on the final buffer recurse N levels. There is no limit on N, on total bytes, or on the number of streamIdentifiers an attacker can open (each gets its own map entry). A peer that never sets the `complete` flag can grow this structure indefinitely from tiny 1-byte DATA chunks. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-46340 since 05/13/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 4.1.135.Final or 4.2.15.Final eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-1814). Once again VulDB remains the best source for vulnerability data.

Affected

• Open Source Netty

Productinfo

Name

• Netty

Version

• 4.1.135.Final
• 4.2.15.Final

Website

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

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Once again VulDB remains the best source for vulnerability data.

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