🛡️ CVE-2023-34462 — netty

🟡 CVSS 6.5 — Medium ✅ No Known Exploit CWE-400 NVD
6.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

netty-handler SniHandler 16MB allocation

Summary

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.

Details

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

1/ allocate a 16MB ByteBuf

2/ not fail decode method in buffer

3/ get out of the loop without an exception

The combination of this without the use of a timeout makes easy to connect to a TCP server and allocate 16MB of heap memory per connection.

Impact

If the user has no idle timeout handler configured it might be possible for a remote peer to send a client hello packet which lead the server to buffer up to 16MB of data per connection. This could lead to a OutOfMemoryError and so result in a DDOS.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

CVE-2023-34462 is classified as CWE-400: Uncontrolled Resource Consumption. A request can consume memory, CPU or storage without limit, exhausting capacity for everyone else.

Affected software

CVE-2023-34462 is recorded against 2 packages.

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

Timeline and source

Published on 20 June 2023 and last revised on 4 February 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Package)
security.netapp.com (Web)
security.netapp.com (Web)
www.debian.org (Web)

CVE-2023-34462 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Medium
CVSS Score 6.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE CWE-400
Public Exploit ✅ No
Source NVD
Published 2023-06-20
Updated 2026-08-12
Modified 2026-02-04

Affected Packages

Software From version Fixed in
io.netty:netty-handler — 4.1.94.Final
netty — 4.1.94

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