---
id: CVE-2025-40281
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sctp: prevent possible shift-out-of-bounds in sctp_transport_update_rto

  syzbot reported a possible shift-out-of-bounds [1]

  Blamed commit added rto_alpha_max and rto_b…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sctp: prevent possible shift-out-of-bounds in sctp_transport_update_rto

  syzbot reported a possible shift-out-of-bounds [1]

  Blamed commit added rto_alpha_max and rto_b…
severity: none
published: '2025-12-06'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T19:10:00.173'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-40281'
references:
  - url: 'https://git.kernel.org/stable/c/0e0413e3315199b23ff4aec295e256034cd0a6e4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1534ff77757e44bcc4b98d0196bc5c0052fce5fa'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1cfa4eac275cc4875755c1303d48a4ddfe507ca8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/834e65be429c0fa4f9bb5945064bd57f18ed2187'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/aaba523dd7b6106526c24b1fd9b5fc35e5aaa88d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/abb086b9a95d0ed3b757ee59964ba3c4e4b2fc1a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d0d858652834dcf531342c82a0428170aa7c2675'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ed71f801249d2350c77a73dca2c03918a15a62fe'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-253495.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
epss: 0.00218
epssPercentile: 0.11364
ingestedAt: '2026-10-15T19:25:46.333Z'
---

## Overview

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

sctp: prevent possible shift-out-of-bounds in sctp_transport_update_rto

syzbot reported a possible shift-out-of-bounds [1]

Blamed commit added rto_alpha_max and rto_beta_max set to 1000.

It is unclear if some sctp users are setting very large rto_alpha
and/or rto_beta.

In order to prevent user regression, perform the test at run time.

Also add READ_ONCE() annotations as sysctl values can change under us.

[1]

UBSAN: shift-out-of-bounds in net/sctp/transport.c:509:41
shift exponent 64 is too large for 32-bit type 'unsigned int'
CPU: 0 UID: 0 PID: 16704 Comm: syz.2.2320 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
  __dump_stack lib/dump_stack.c:94 [inline]
  dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:120
  ubsan_epilogue lib/ubsan.c:233 [inline]
  __ubsan_handle_shift_out_of_bounds+0x27f/0x420 lib/ubsan.c:494
  sctp_transport_update_rto.cold+0x1c/0x34b net/sctp/transport.c:509
  sctp_check_transmitted+0x11c4/0x1c30 net/sctp/outqueue.c:1502
  sctp_outq_sack+0x4ef/0x1b20 net/sctp/outqueue.c:1338
  sctp_cmd_process_sack net/sctp/sm_sideeffect.c:840 [inline]
  sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1372 [inline]

## Remediation

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