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CVE-2026-23331

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: udp: Unhash auto-bound connected sk from 4-tuple hash table when disconnected.

Published Mar 25, 2026EPSS 0.12%

Overview

CVE-2026-23331 is a medium-severity vulnerability. It was published on March 25, 2026 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

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().

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/3b8f104880c104151f8c30f2f89df81fb59a286cRefgit.kernel.org/stable/c/6996a2d2d0a64808c19c98002aeb5d9d1b2df6a4Refgit.kernel.org/stable/c/b955350778b8715e1b7885179979b3a68221c0fb

How CyberStrike helps

Frequently asked questions

What is CVE-2026-23331?

CVE-2026-23331 is a medium-severity vulnerability. It was published on March 25, 2026 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2026-23331?

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-23331?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-23331?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-23331 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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