Linux Kernel up to 6.18.16/6.19.6/7.0-rc2 udp bind privilege escalation

Summaryinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.18.16/6.19.6/7.0-rc2. This affects the function bind of the component udp. The manipulation leads to an unknown weakness. This vulnerability is traded as CVE-2026-23331. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.18.16/6.19.6/7.0-rc2. This issue affects the function bind of the component udp. The impact remains unknown. The summary by CVE is:

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().

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-23331 since 01/13/2026. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/17/2026).

The vulnerability scanner Nessus provides a plugin with the ID 304077 (Linux Distros Unpatched Vulnerability : CVE-2026-23331), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.18.17, 6.19.7 or 7.0-rc3 eliminates this vulnerability. Applying the patch b955350778b8715e1b7885179979b3a68221c0fb/3b8f104880c104151f8c30f2f89df81fb59a286c/6996a2d2d0a64808c19c98002aeb5d9d1b2df6a4 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (304077) and CERT Bund (WID-SEC-2026-0861). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Google Cloud Platform
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• Open Source Linux Kernel
• RESF Rocky Linux

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.19.0
• 6.19.1
• 6.19.2
• 6.19.3
• 6.19.4
• 6.19.5
• 6.19.6
• 7.0-rc1
• 7.0-rc2

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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