Linux Kernel up to 6.17-rc2 br_multicast_query_expired denial of service

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5.0$0-$5k0.00

Summaryinfo

A vulnerability identified as critical has been detected in Linux Kernel up to 6.17-rc2. The affected element is the function br_multicast_query_expired. Performing a manipulation results in denial of service. This vulnerability was named CVE-2025-39773. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.17-rc2. This affects the function br_multicast_query_expired. The manipulation with an unknown input leads to a denial of service vulnerability. CWE is classifying the issue as CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. This is going to have an impact on availability. The summary by CVE is:

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.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2025-39773 since 04/16/2025. The exploitability is told to be difficult. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 264769 (Linux Distros Unpatched Vulnerability : CVE-2025-39773), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.15.190, 6.1.149, 6.6.103, 6.12.44, 6.16.4 or 6.17-rc3 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (264769) and CERT Bund (WID-SEC-2025-2040). Be aware that VulDB is the high quality source for vulnerability data.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Google Cloud Platform
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Fedora Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Open Source Linux Kernel
  • Proxmox Virtual Environment
  • Proxmox Backup Server
  • Dell Secure Connect Gateway
  • IBM QRadar SIEM

Productinfo

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Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.1
VulDB Meta Temp Score: 5.0

VulDB Base Score: 4.8
VulDB Temp Score: 4.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Denial of service
CWE: CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 264769
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2025-39773

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.15.190/6.1.149/6.6.103/6.12.44/6.16.4/6.17-rc3
Patch: git.kernel.org

Timelineinfo

04/16/2025 CVE reserved
09/11/2025 +148 days Advisory disclosed
09/11/2025 +0 days VulDB entry created
01/16/2026 +127 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-39773 (🔒)
GCVE (CVE): GCVE-0-2025-39773
GCVE (VulDB): GCVE-100-323703
CERT Bund: WID-SEC-2025-2040 - Linux Kernel: Mehrere Schwachstellen erm&ouml;glichen Denial of Service

Entryinfo

Created: 09/11/2025 19:39
Updated: 01/16/2026 22:20
Changes: 09/11/2025 19:39 (57), 09/12/2025 21:39 (7), 09/14/2025 19:39 (2), 11/08/2025 13:19 (1), 11/16/2025 01:16 (1), 01/16/2026 22:20 (12)
Complete: 🔍
Cache ID: 216::103

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