---
id: CVE-2026-68297
title: 'tipc: fix u16 MTU truncation in media and bearer MTU validation'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  tipc: fix u16 MTU truncation in media and bearer MTU validation

  Both TIPC_NL_MEDIA_SET and TIPC_NL_BEARER_SET accept user-supplied
  MTU values but only enforce a minimu…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 901271e0403af638c224987c2a4e55cebade7e91 <
    8bfdfe0dbb36a650b7c4dec1aeae078319938a0b
  - >-
    Linux >= 901271e0403af638c224987c2a4e55cebade7e91 <
    dc4b577a083b361d25e118dc96d8281255ebe22c
  - >-
    Linux >= 901271e0403af638c224987c2a4e55cebade7e91 <
    dfdfd987f1917c84766e097a6120a1f3f1634940
  - >-
    Linux >= 901271e0403af638c224987c2a4e55cebade7e91 <
    f02334a9e378f7e07232b26dc3d2ab353339f040
  - >-
    Linux >= 901271e0403af638c224987c2a4e55cebade7e91 <
    f4013598b69457dbea350df52e52daea6faef8eb
  - >-
    Linux >= 901271e0403af638c224987c2a4e55cebade7e91 <
    1b8fb5a20508bfb0db854e01214888c761b3a911
  - >-
    Linux >= 901271e0403af638c224987c2a4e55cebade7e91 <
    c1cda72f6acec02ebd45d913bf8527ff77336ba6
  - >-
    Linux >= 901271e0403af638c224987c2a4e55cebade7e91 <
    9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8
  - Linux 4.18
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T15:46:47.440623Z'
published: '2026-08-10'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:53:06.926Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-68297'
references:
  - url: 'https://git.kernel.org/stable/c/8bfdfe0dbb36a650b7c4dec1aeae078319938a0b'
  - url: 'https://git.kernel.org/stable/c/dc4b577a083b361d25e118dc96d8281255ebe22c'
  - url: 'https://git.kernel.org/stable/c/dfdfd987f1917c84766e097a6120a1f3f1634940'
  - url: 'https://git.kernel.org/stable/c/f02334a9e378f7e07232b26dc3d2ab353339f040'
  - url: 'https://git.kernel.org/stable/c/f4013598b69457dbea350df52e52daea6faef8eb'
  - url: 'https://git.kernel.org/stable/c/1b8fb5a20508bfb0db854e01214888c761b3a911'
  - url: 'https://git.kernel.org/stable/c/c1cda72f6acec02ebd45d913bf8527ff77336ba6'
  - url: 'https://git.kernel.org/stable/c/9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8'
tags:
  - cve.org
epss: 0.00129
epssPercentile: 0.02277
ingestedAt: '2026-10-16T17:24:46.855Z'
---

## Overview

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

tipc: fix u16 MTU truncation in media and bearer MTU validation

Both TIPC_NL_MEDIA_SET and TIPC_NL_BEARER_SET accept user-supplied
MTU values but only enforce a minimum bound, not a maximum. When a user
sets the MTU to a value exceeding U16_MAX (65535), it passes validation
but is silently truncated when assigned to u16 fields l->mtu and
l->advertised_mtu in tipc_link_create(). Values like 65536 (0x10000)
truncate to 0, causing a division by zero in tipc_link_set_queue_limits()
which computes TIPC_MAX_PUBL / (l->mtu / ITEM_SIZE). Other overflowing
values (e.g. 65537-131071) produce small incorrect MTU values, resulting
in link malfunction behaviors.

Crash stack (triggered as unprivileged user via user namespace):

  tipc_link_set_queue_limits  net/tipc/link.c:2531
  tipc_link_create            net/tipc/link.c:520
  tipc_node_check_dest        net/tipc/node.c:1279
  tipc_disc_rcv               net/tipc/discover.c:252
  tipc_rcv                    net/tipc/node.c:2129
  tipc_udp_recv               net/tipc/udp_media.c:392

Two independent paths lack the upper bound check:
1. tipc_udp_mtu_bad() -- called from __tipc_nl_media_set() (MEDIA_SET)
2. inline check in __tipc_nl_bearer_set() at bearer.c:1160 (BEARER_SET)

Fix both by rejecting MTU values above U16_MAX.

## Affected

- `Linux >= 901271e0403af638c224987c2a4e55cebade7e91 < 8bfdfe0dbb36a650b7c4dec1aeae078319938a0b`
- `Linux >= 901271e0403af638c224987c2a4e55cebade7e91 < dc4b577a083b361d25e118dc96d8281255ebe22c`
- `Linux >= 901271e0403af638c224987c2a4e55cebade7e91 < dfdfd987f1917c84766e097a6120a1f3f1634940`
- `Linux >= 901271e0403af638c224987c2a4e55cebade7e91 < f02334a9e378f7e07232b26dc3d2ab353339f040`
- `Linux >= 901271e0403af638c224987c2a4e55cebade7e91 < f4013598b69457dbea350df52e52daea6faef8eb`
- `Linux >= 901271e0403af638c224987c2a4e55cebade7e91 < 1b8fb5a20508bfb0db854e01214888c761b3a911`
- `Linux >= 901271e0403af638c224987c2a4e55cebade7e91 < c1cda72f6acec02ebd45d913bf8527ff77336ba6`
- `Linux >= 901271e0403af638c224987c2a4e55cebade7e91 < 9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8`
- `Linux 4.18`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.