CVE-2026-23331: Linux Kernel

Medium severity, CVSS 5.5. EPSS: 0.1% chance of exploitation in the next 30 days.

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().

Affected products

• Linux Linux Kernel: from 6.13.1, before 6.18.17 (fixed in 6.18.17); from 6.19, before 6.19.7 (fixed in 6.19.7); version 6.13 only; version 7.0 only

Published 2026-03-25. Last modified 2026-06-17.