---
id: CVE-2025-39773
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: bridge: fix soft lockup in br_multicast_query_expired()

  When set multicast_query_interval to a large value, the local variable
  'time' in br_multicast_send_query()…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: bridge: fix soft lockup in br_multicast_query_expired()

  When set multicast_query_interval to a large value, the local variable
  'time' in br_multicast_send_query()…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-667
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.34, < 5.15.190'
  - 'linux_kernel >= 5.16, < 6.1.149'
  - 'linux_kernel >= 6.2, < 6.6.103'
  - 'linux_kernel >= 6.7, < 6.12.44'
  - 'linux_kernel >= 6.13, < 6.16.4'
  - linux_kernel = 6.17
  - debian_linux = 11.0
patched:
  - linux_kernel 6.16.4
published: '2025-09-11'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:18:00.563'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-39773'
references:
  - url: 'https://git.kernel.org/stable/c/34171b9e53bd1dc264f5556579f2b04f04435c73'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/43e281fde5e76a866a4d10780c35023f16c0e432'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5bf5fce8a0c2a70d063af778fdb5b27238174cdd'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/96476b043efb86a94f2badd260f7f99c97bd5893'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bdb19cd0de739870bb3494c815138b9dc30875c4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d1547bf460baec718b3398365f8de33d25c5f36f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-032379.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-082556.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-457936.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00123
epssPercentile: 0.02077
ingestedAt: '2026-09-08T15:33:26.997Z'
---

## Overview

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

net: bridge: fix soft lockup in br_multicast_query_expired()

When set multicast_query_interval to a large value, the local variable
'time' in br_multicast_send_query() may overflow. If the time is smaller
than jiffies, the timer will expire immediately, and then call mod_timer()
again, which creates a loop and may trigger the following soft lockup
issue.

  watchdog: BUG: soft lockup - CPU#1 stuck for 221s! [rb_consumer:66]
  CPU: 1 UID: 0 PID: 66 Comm: rb_consumer Not tainted 6.16.0+ #259 PREEMPT(none)
  Call Trace:
   <IRQ>
   __netdev_alloc_skb+0x2e/0x3a0
   br_ip6_multicast_alloc_query+0x212/0x1b70
   __br_multicast_send_query+0x376/0xac0
   br_multicast_send_query+0x299/0x510
   br_multicast_query_expired.constprop.0+0x16d/0x1b0
   call_timer_fn+0x3b/0x2a0
   __run_timers+0x619/0x950
   run_timer_softirq+0x11c/0x220
   handle_softirqs+0x18e/0x560
   __irq_exit_rcu+0x158/0x1a0
   sysvec_apic_timer_interrupt+0x76/0x90
   </IRQ>

This issue can be reproduced with:
  ip link add br0 type bridge
  echo 1 > /sys/class/net/br0/bridge/multicast_querier
  echo 0xffffffffffffffff >
  	/sys/class/net/br0/bridge/multicast_query_interval
  ip link set dev br0 up

The multicast_startup_query_interval can also cause this issue. Similar to
the commit 99b40610956a ("net: bridge: mcast: add and enforce query
interval minimum"), add check for the query interval maximum to fix this
issue.

## Affected

- `linux_kernel >= 2.6.34, < 5.15.190`
- `linux_kernel >= 5.16, < 6.1.149`
- `linux_kernel >= 6.2, < 6.6.103`
- `linux_kernel >= 6.7, < 6.12.44`
- `linux_kernel >= 6.13, < 6.16.4`
- `linux_kernel = 6.17`
- `debian_linux = 11.0`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.16.4`