Answer in brief
CVE-2023-34462 records a Medium severity (CVSS 6.5) vulnerability in netty-handler SniHandler 16MB allocation. The current sources do not mark it as known exploited. The current feed maps io.netty:netty-handler (maven). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps io.netty:netty-handler (maven). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| io.netty:netty-handlermaven | >=0 <4.1.94.Final | 4.1.94.Final |
Published upstream
Jun 20, 2023
Evidence: source:osv:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:recordFirst seen by HOL
Sep 10, 2026
### 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.
Quoted source text, attributed separately from HOL analysis.