CVE-2026-74434

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

rxrpc: Don't move a peeked OOB message onto the pending queue

rxrpcrecvmsgoob() takes a received oob message off recvmsg_oobq and,

if a response is needed, moves it onto the pending_oobq tree. However,

only the unlink from recvmsgoobq is guarded by MSGPEEK; the move onto

pending_oobq always runs.

As a result, reading a challenge with MSG_PEEK leaves the skb on

recvmsgoobq while also adding it to pendingoobq. Since struct

sk_buff's rbnode shares storage with its next and prev pointers,

rbinsertcolor() overwrites the list linkage, and the skb, which holds

a single reference, becomes reachable from both queues at once.

When the socket is closed both queues are drained in turn. While

draining recvmsgoobq, skbunlink() follows the next and prev

pointers that rbnode has overwritten and writes to a bad address. Also,

as the skb holds a single reference but is freed from each queue, both

the skb and the connection reference it holds are released twice. This

leads to memory corruption and to a use-after-free caused by the

connection refcount underflow.

MSG_PEEK does not consume the message from the queue, so only unlink it

from recvmsgoobq and then move it onto pendingoobq or free it when

the message is actually consumed.