---
id: CVE-2023-53517
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  tipc: do not update mtu if msg_max is too small in mtu negotiation

  When doing link mtu negotiation, a malicious peer may send Activate msg
  with a very small mtu, e.g
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  tipc: do not update mtu if msg_max is too small in mtu negotiation

  When doing link mtu negotiation, a malicious peer may send Activate msg
  with a very small mtu, e.g. …
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-190
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 4.1, < 5.10.181'
  - 'linux_kernel >= 5.11, < 5.15.113'
  - 'linux_kernel >= 5.16, < 6.1.30'
  - 'linux_kernel >= 6.2, < 6.3.4'
  - linux_kernel = 6.4
patched:
  - linux_kernel 6.3.4
published: '2025-10-01'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:17:41.720'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-53517'
references:
  - url: 'https://git.kernel.org/stable/c/1dd7ae5e0cf5a56e513f7ab7ab9570b7496281d2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/259683001d7e879fea4b42084fb6560dd9408a7e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2bd4ff4ffb92113f8acd04dbaed83269172c24b4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/56077b56cd3fb78e1c8619e29581ba25a5c55e86'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/575e84d90a74c0b091b3417ba763ebb237aa0a8c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2023/cve-2023-53517.json
  - url: 'https://access.redhat.com/security/cve/CVE-2023-53517'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2400721'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2023-53517'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2023-53517'
  - url: >-
      https://lore.kernel.org/linux-cve-announce/2025100132-CVE-2023-53517-da77@gregkh/T
  - url: 'https://access.redhat.com/errata/RHSA-2023:7077'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
  - cve.org
  - score-dispute
epss: 0.00305
epssPercentile: 0.23158
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-15T21:35:14.831985Z'
scores:
  nvd: 9.8
  vendor: 5.5
  cna: 9.8
ingestedAt: '2026-10-15T22:48:25.405Z'
---

## Overview

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

tipc: do not update mtu if msg_max is too small in mtu negotiation

When doing link mtu negotiation, a malicious peer may send Activate msg
with a very small mtu, e.g. 4 in Shuang's testing, without checking for
the minimum mtu, l->mtu will be set to 4 in tipc_link_proto_rcv(), then
n->links[bearer_id].mtu is set to 4294967228, which is a overflow of
'4 - INT_H_SIZE - EMSG_OVERHEAD' in tipc_link_mss().

With tipc_link.mtu = 4, tipc_link_xmit() kept printing the warning:

 tipc: Too large msg, purging xmit list 1 5 0 40 4!
 tipc: Too large msg, purging xmit list 1 15 0 60 4!

And with tipc_link_entry.mtu 4294967228, a huge skb was allocated in
named_distribute(), and when purging it in tipc_link_xmit(), a crash
was even caused:

  general protection fault, probably for non-canonical address 0x2100001011000dd: 0000 [#1] PREEMPT SMP PTI
  CPU: 0 PID: 0 Comm: swapper/0 Kdump: loaded Not tainted 6.3.0.neta #19
  RIP: 0010:kfree_skb_list_reason+0x7e/0x1f0
  Call Trace:
   <IRQ>
   skb_release_data+0xf9/0x1d0
   kfree_skb_reason+0x40/0x100
   tipc_link_xmit+0x57a/0x740 [tipc]
   tipc_node_xmit+0x16c/0x5c0 [tipc]
   tipc_named_node_up+0x27f/0x2c0 [tipc]
   tipc_node_write_unlock+0x149/0x170 [tipc]
   tipc_rcv+0x608/0x740 [tipc]
   tipc_udp_recv+0xdc/0x1f0 [tipc]
   udp_queue_rcv_one_skb+0x33e/0x620
   udp_unicast_rcv_skb.isra.72+0x75/0x90
   __udp4_lib_rcv+0x56d/0xc20
   ip_protocol_deliver_rcu+0x100/0x2d0

This patch fixes it by checking the new mtu against tipc_bearer_min_mtu(),
and not updating mtu if it is too small.

## Affected

- `linux_kernel >= 4.1, < 5.10.181`
- `linux_kernel >= 5.11, < 5.15.113`
- `linux_kernel >= 5.16, < 6.1.30`
- `linux_kernel >= 6.2, < 6.3.4`
- `linux_kernel = 6.4`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.3.4`

## Vendor advisories

- **RHSA-2023:7077** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat CodeReady Linux Builder (v. 8) · released 2023-11-14 · [advisory](https://access.redhat.com/errata/RHSA-2023:7077)
- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2023/cve-2023-53517.json)