CVE-2026-31696

In the Linux kernel, the following vulnerability has been resolved:

rxrpc: Fix missing validation of ticket length in non-XDR key preparsing

In rxrpcpreparse(), there are two paths for parsing key payloads: the XDR path (for large payloads) and the non-XDR path (for payloads <= 28 bytes). While the XDR path (rxrpcpreparsexdrrxkad()) correctly validates the ticket length against AFSTOKENRKTIX_MAX, the non-XDR path fails to do so.

This allows an unprivileged user to provide a very large ticket length. When this key is later read via rxrpcread(), the total token size (toksize) calculation results in a value that exceeds AFSTOKENLENGTHMAX, triggering a WARNON().

[ 2001.302904] WARNING: CPU: 2 PID: 2108 at net/rxrpc/key.c:778 rxrpc_read+0x109/0x5c0 [rxrpc]

Fix this by adding a check in the non-XDR parsing path of rxrpcpreparse() to ensure the ticket length does not exceed AFSTOKENRKTIXMAX, bringing it into parity with the XDR parsing logic.