CVE-2023-34462 is a medium-severity uncontrolled resource consumption vulnerability in io.netty:netty-handler (maven), affecting versions < 4.1.94.Final. It is fixed in 4.1.94.Final.
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.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2023-34462 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (4.1.94.Final). Upgrading removes the vulnerable code path.
maven
io.netty:netty-handler (< 4.1.94.Final)io.netty:netty-handler → 4.1.94.Final (maven)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2023-34462 is reachable in your applications. Explore open-source security for your team.
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Upgrade io.netty:netty-handler to 4.1.94.Final or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2023-34462 is a medium-severity uncontrolled resource consumption vulnerability in io.netty:netty-handler (maven), affecting versions < 4.1.94.Final. It is fixed in 4.1.94.Final. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
CVE-2023-34462 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
io.netty:netty-handler (maven) versions < 4.1.94.Final is affected.
Yes. CVE-2023-34462 is fixed in 4.1.94.Final. Upgrade to this version or later.
Whether CVE-2023-34462 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade io.netty:netty-handler to 4.1.94.Final or later.