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Incorrect Check of Function Return Value Affecting kernel-rt package, versions *

Severity

 Recommended
0.0
medium
0
10

Based on CentOS security rating.

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  • Snyk IDSNYK-CENTOS7-KERNELRT-16162800
  • published23 Apr 2026
  • disclosed22 Apr 2026
Report a new vulnerability Found a mistake?

Introduced: 22 Apr 2026

NewCVE-2026-31503  (opens in a new tab)
CWE-253  (opens in a new tab)

How to fix?

There is no fixed version for Centos:7 kernel-rt.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt package and not the kernel-rt package as distributed by Centos. See How to fix? for Centos:7 relevant fixed versions and status.

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

udp: Fix wildcard bind conflict check when using hash2

When binding a udp_sock to a local address and port, UDP uses two hashes (udptable->hash and udptable->hash2) for collision detection. The current code switches to "hash2" when hslot->count > 10.

"hash2" is keyed by local address and local port. "hash" is keyed by local port only.

The issue can be shown in the following bind sequence (pseudo code):

bind(fd1, "[fd00::1]:8888") bind(fd2, "[fd00::2]:8888") bind(fd3, "[fd00::3]:8888") bind(fd4, "[fd00::4]:8888") bind(fd5, "[fd00::5]:8888") bind(fd6, "[fd00::6]:8888") bind(fd7, "[fd00::7]:8888") bind(fd8, "[fd00::8]:8888") bind(fd9, "[fd00::9]:8888") bind(fd10, "[fd00::10]:8888")

/* Correctly return -EADDRINUSE because "hash" is used

  • instead of "hash2". udp_lib_lport_inuse() detects the
  • conflict. */ bind(fail_fd, "[::]:8888")

/* After one more socket is bound to "[fd00::11]:8888",

  • hslot->count exceeds 10 and "hash2" is used instead. / bind(fd11, "[fd00::11]:8888") bind(fail_fd, "[::]:8888") / succeeds unexpectedly */

The same issue applies to the IPv4 wildcard address "0.0.0.0" and the IPv4-mapped wildcard address "::ffff:0.0.0.0". For example, if there are existing sockets bound to "192.168.1.[1-11]:8888", then binding "0.0.0.0:8888" or "[::ffff:0.0.0.0]:8888" can also miss the conflict when hslot->count > 10.

TCP inet_csk_get_port() already has the correct check in inet_use_bhash2_on_bind(). Rename it to inet_use_hash2_on_bind() and move it to inet_hashtables.h so udp.c can reuse it in this fix.

CVSS Base Scores

version 3.1