NuytsTech Security

CVE-2026-23331

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

udp: Unhash auto-bound connected sk from 4-tuple hash table when disconnected.

Let’s say we bind() an UDP socket to the wildcard address with a
non-zero port, connect() it to an address, and disconnect it from
the address.

bind() sets SOCK_BINDPORT_LOCK on sk->sk_userlocks (but not
SOCK_BINDADDR_LOCK), and connect() calls udp_lib_hash4() to put
the socket into the 4-tuple hash table.

Then, __udp_disconnect() calls sk->sk_prot->rehash(sk).

It computes a new hash based on the wildcard address and moves
the socket to a new slot in the 4-tuple hash table, leaving a
garbage in the chain that no packet hits.

Let’s remove such a socket from 4-tuple hash table when disconnected.

Note that udp_sk(sk)->udp_portaddr_hash needs to be udpated after
udp_hash4_dec(hslot2) in udp_unhash4().

More information : https://git.kernel.org/stable/c/3b8f104880c104151f8c30f2f89df81fb59a286c

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