CVE-2023-34462mediumCWE-400

CVE-2023-34462: medium-severity vulnerability in netty

netty-handler SniHandler 16MB allocation

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 6.5epss 2.5%
In short

The SniHandler in Netty can be tricked into allocating up to 16MB of memory for each connection during TLS handshake, allowing attackers to exhaust server memory by opening many connections without proper timeout settings.

Technical detail

The SniHandler lacks validation on the ClientHello packet size and allocates a ByteBuf based on untrusted client-supplied values, enabling a resource exhaustion attack. An attacker can send crafted TLS handshake packets to cause excessive heap allocation on servers without idle timeouts, leading to denial of service through memory exhaustion.

Summary generated and translated by AI from the official 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.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Affected products
netty · netty
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