GHSA-x4gw-5cx5-pgmh
Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| Maven | io.netty:netty-handler | >= 4.2.0.Final, < 4.2.15.Final | 4.2.15.Final |
| Maven | io.netty:netty-handler | < 4.1.135.Final | 4.1.135.Final |
Details
As written in the advisory (Markdown source, shown as plain text).
SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates `ctx.alloc().buffer(handshakeLength)` (line 161). The guard at line 140 is `handshakeLength > maxClientHelloLength && maxClientHelloLength != 0`, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes.
References
External links from the advisory. They lead to third-party sites.