CVE-2025-39773: net: bridge: fix soft lockup in br_multicast_query_expired()

Q: What is the severity of CVE-2025-39773?

CVE-2025-39773 is considered a medium severity vulnerability due to potential local disruption in the Linux kernel.

Q: How do I fix CVE-2025-39773?

To fix CVE-2025-39773, update your Linux kernel to a version that includes the patch for this vulnerability.

Q: What does CVE-2025-39773 affect?

CVE-2025-39773 affects the Linux kernel version 6.16.0 and later implementations that use the bridge multicast query features.

Q: What are the potential consequences of CVE-2025-39773?

The potential consequences of CVE-2025-39773 include a local system lockup when handling multicast queries under specific conditions.

Q: In which Linux kernel functions does CVE-2025-39773 manifest?

CVE-2025-39773 manifests in the br_multicast_query_expired() and br_multicast_send_query() functions within the kernel networking code.

Published Sep 11, 2025

Updated

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

net: bridge: fix soft lockup in brmulticastqueryexpired()

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

watchdog: BUG: soft lockup - CPU#1 stuck for 221s! [rbconsumer:66] CPU: 1 UID: 0 PID: 66 Comm: rbconsumer Not tainted 6.16.0+ #259 PREEMPT(none) Call Trace: <IRQ> netdevallocskb+0x2e/0x3a0 brip6multicastallocquery+0x212/0x1b70 brmulticastsendquery+0x376/0xac0 brmulticastsendquery+0x299/0x510 brmulticastqueryexpired.constprop.0+0x16d/0x1b0 calltimerfn+0x3b/0x2a0 runtimers+0x619/0x950 runtimersoftirq+0x11c/0x220 handlesoftirqs+0x18e/0x560 irqexitrcu+0x158/0x1a0 sysvecapictimerinterrupt+0x76/0x90 </IRQ>

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

The multicaststartupqueryinterval 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 Software

246 affected componentsFixes available

Linux Linux kernel>=6.16.0

Microsoft azl3 kernel 6.6.96.2-2

Patch available

Microsoft cbl2 kernel 5.15.186.1-1

Patch available

Linux Linux kernel>=2.6.34<5.15.190

Linux Linux kernel>=5.16<6.1.149

Linux Linux kernel>=6.2<6.6.103

Linux Linux kernel>=6.7<6.12.44

Linux Linux kernel>=6.13<6.16.4

Linux Linux kernel=6.17-rc1

Linux Linux kernel=6.17-rc2

Debian Debian Linux=11.0

debian/linux<6.1.153-1

6.1.153-1

debian/linux<6.12.48-1

6.12.48-1

debian/linux<6.16.5-1

6.16.5-1

linux/kernel>=2.6.34<5.15.190

5.15.190

linux/kernel>=5.16.0<6.1.149

6.1.149

linux/kernel>=6.2.0<6.6.103

6.6.103

linux/kernel>=6.7.0<6.12.44

6.12.44

linux/kernel>=6.13.0<6.16.4

6.16.4

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-azure*

ubuntu/linux-lts-xenial*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-hwe*

ubuntu/linux-azure*

ubuntu/linux-gcp*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-kvm*

ubuntu/linux-oracle*

ubuntu/linux-fips*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-aws-5.4*

ubuntu/linux-azure*

ubuntu/linux-azure-4.15*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-4.15*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gcp-5.4*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-5.4*

ubuntu/linux-hwe-edge*

ubuntu/linux-ibm-5.4*

ubuntu/linux-kvm*

ubuntu/linux-oem*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4*

ubuntu/linux-raspi-5.4*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15<5.15.0-1097.104~20.04.1

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ubuntu/linux-aws-5.8*

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ubuntu/linux-azure-5.11*

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ubuntu/linux-gcp-5.15<5.15.0-1097.106~20.04.1

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ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

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ubuntu/linux-gkeop*

ubuntu/linux-gkeop-5.15*

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ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm*

ubuntu/linux-ibm-5.15<5.15.0-1091.94~20.04.1

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ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15<5.15.0-1092.98~20.04.1

5.15.0-1092.98~20.04.1

ubuntu/linux-iot*

ubuntu/linux-kvm*

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-163.173~20.04.1

5.15.0-163.173~20.04.1

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1049.49~20.04.1

5.15.0-1049.49~20.04.1

ubuntu/linux-oem-5.10*

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ubuntu/linux-oem-5.6*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.15<5.15.0-1094.100~20.04.1

5.15.0-1094.100~20.04.1

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15<5.15.0-1092.96~20.04.1

5.15.0-1092.96~20.04.1

ubuntu/linux-riscv-5.8*

ubuntu/linux-xilinx-zynqmp*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.15.0-163.173

5.15.0-163.173

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1097.104

5.15.0-1097.104

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1046.49~22.04.1

6.8.0-1046.49~22.04.1

ubuntu/linux-azure<5.15.0-1101.110

5.15.0-1101.110

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1051.57~22.04.1

6.8.0-1051.57~22.04.1

ubuntu/linux-azure-fde<5.15.0-1102.111.1

5.15.0-1102.111.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1046.53~22.04.1

6.8.0-1046.53~22.04.1

ubuntu/linux-gcp<5.15.0-1097.106

5.15.0-1097.106

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1047.50~22.04.2

6.8.0-1047.50~22.04.2

ubuntu/linux-gke<5.15.0-1093.99

5.15.0-1093.99

ubuntu/linux-gkeop<5.15.0-1080.88

5.15.0-1080.88

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-100.100~22.04.1

6.8.0-100.100~22.04.1

ubuntu/linux-ibm<5.15.0-1091.94

5.15.0-1091.94

ubuntu/linux-ibm-6.8<6.8.0-1044.44~22.04.1

6.8.0-1044.44~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1092.98

5.15.0-1092.98

ubuntu/linux-kvm<5.15.0-1089.94

5.15.0-1089.94

ubuntu/linux-lowlatency<5.15.0-163.173

5.15.0-163.173

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-100.100.1~22.04.1

6.8.0-100.100.1~22.04.1

ubuntu/linux-nvidia<5.15.0-1092.93

5.15.0-1092.93

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1046.49~22.04.1

6.8.0-1046.49~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1049.49

5.15.0-1049.49

ubuntu/linux-nvidia-tegra-igx<5.15.0-1038.38

5.15.0-1038.38

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1094.100

5.15.0-1094.100

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1043.44~22.04.1

6.8.0-1043.44~22.04.1

ubuntu/linux-raspi<5.15.0-1091.94

5.15.0-1091.94

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-100.100~22.04.1

6.8.0-100.100~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1061.65

5.15.0-1061.65

ubuntu/linux-bluefield<5.15.0-1081.83

5.15.0-1081.83

ubuntu/linux-intel-iot-realtime<5.15.0-1089.91

5.15.0-1089.91

ubuntu/linux-realtime<5.15.0-1096.105

5.15.0-1096.105

ubuntu/linux-realtime-6.8<6.8.1-1041.42~22.04.1

6.8.1-1041.42~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1097.104+fips1

5.15.0-1097.104+fips1

ubuntu/linux-azure-fips<5.15.0-1101.110+fips1

5.15.0-1101.110+fips1

ubuntu/linux-fips<5.15.0-163.173+fips1

5.15.0-163.173+fips1

ubuntu/linux-gcp-fips<5.15.0-1097.106+fips1

5.15.0-1097.106+fips1

ubuntu/linux<6.8.0-100.100

6.8.0-100.100

ubuntu/linux-aws<6.8.0-1046.49

6.8.0-1046.49

ubuntu/linux-aws-6.14*

ubuntu/linux-azure<6.8.0-1046.52

6.8.0-1046.52

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-fde<6.8.0-1046.53

6.8.0-1046.53

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-nvidia<6.8.0-1039.42

6.8.0-1039.42

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1047.50

6.8.0-1047.50

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gke<6.8.0-1043.48

6.8.0-1043.48

ubuntu/linux-gkeop<6.8.0-1030.33

6.8.0-1030.33

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-ibm<6.8.0-1044.44

6.8.0-1044.44

ubuntu/linux-intel*

ubuntu/linux-lowlatency<6.8.0-100.100.1

6.8.0-100.100.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1046.49

6.8.0-1046.49

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-lowlatency<6.8.0-1046.49.1

6.8.0-1046.49.1

ubuntu/linux-nvidia-tegra<6.8.0-1020.20

6.8.0-1020.20

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1043.44

6.8.0-1043.44

ubuntu/linux-oracle-6.14*

ubuntu/linux-raspi<6.8.0-1047.51

6.8.0-1047.51

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-xilinx<6.8.0-1023.24

6.8.0-1023.24

ubuntu/linux-bluefield<6.8.0-1016.20

6.8.0-1016.20

ubuntu/linux-raspi-realtime<6.8.0-2037.38

6.8.0-2037.38

ubuntu/linux-realtime<6.8.1-1041.42

6.8.1-1041.42

ubuntu/linux-realtime-6.14*

ubuntu/linux-aws-fips<6.8.0-1046.49+fips1

6.8.0-1046.49+fips1

ubuntu/linux-azure-fips<6.8.0-1046.52+fips1

6.8.0-1046.52+fips1

ubuntu/linux-fips<6.8.0-100.100+fips1

6.8.0-100.100+fips1

ubuntu/linux-gcp-fips<6.8.0-1047.50+fips1

6.8.0-1047.50+fips1

ubuntu/linux-azure-fde*

ubuntu/linux-vmware*

debian/linux

6.1.176-16.1.190-16.12.107-16.12.116-17.2.15-17.3.4-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
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Fixed in 6.1.153-1
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Fixed in 6.16.5-1
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Fixed in 5.15.190
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Fixed in 6.1.149
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Fixed in 6.6.103
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Fixed in 6.12.44
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Fixed in 5.15.0-1097.104~20.04.1
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Fixed in 5.15.0-1102.111~20.04.1
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Fixed in 5.15.0-1097.106~20.04.1
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Fixed in 5.15.0-163.173~20.04.1
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Fixed in 5.15.0-1091.94~20.04.1
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Fixed in 5.15.0-1092.98~20.04.1
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Fixed in 5.15.0-163.173~20.04.1
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Fixed in 5.15.0-1049.49~20.04.1
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Fixed in 5.15.0-1094.100~20.04.1
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Fixed in 5.15.0-1092.96~20.04.1
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Fixed in 5.15.0-163.173
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Fixed in 5.15.0-1097.104
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Fixed in 6.8.0-1046.49~22.04.1
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Fixed in 5.15.0-1101.110
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Fixed in 5.15.0-1102.111.1
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Fixed in 6.8.0-1046.53~22.04.1
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Fixed in 5.15.0-1097.106
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Fixed in 5.15.0-1093.99
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Fixed in 5.15.0-1091.94
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Fixed in 5.15.0-1096.105
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Fixed in 6.8.1-1041.42~22.04.1
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Fixed in 6.8.0-1043.48
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Fixed in 6.8.0-1044.44
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Fixed in 6.8.0-1046.49.1
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Fixed in 6.8.0-1020.20
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Fixed in 6.8.0-1043.44
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Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.8.0-1047.51
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Upgrade ubuntu/linux-xilinx to a version that resolves this vulnerability.
Fixed in 6.8.0-1023.24
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Fixed in 6.8.0-1016.20
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Fixed in 6.8.0-2037.38
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Fixed in 6.8.1-1041.42
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Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1046.49+fips1
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Fixed in 6.8.0-1046.52+fips1
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Fixed in 6.8.0-100.100+fips1
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Fixed in 6.8.0-1047.50+fips1
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Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.116-1Fixed in 7.2.15-1Fixed in 7.3.4-1
Configuration
Add and enforce a maximum for the multicast query intervals to prevent timer overflow and soft lockups.
Linux bridge multicast multicast_query_interval and multicast_startup_query_interval = enforce a maximum

Event History

Sep 11, 2025

CVE Published

via MITRE·04:56 PM

Data Sourced

via MITRE·04:56 PM

Description

Data Sourced

via OSV·04:56 PM

DescriptionAffected Software

Data Sourced

via NVD·05:15 PM

RemedyDescriptionSeverityWeaknessAffected Software

Sep 13, 2025

Data Sourced

via Microsoft·01:02 AM

DescriptionSeverityWeaknessAffected Software

Nov 11, 2026

Data Sourced

via OSV·09:39 AM

Severity

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

DLA-4328-1

Frequently Asked Questions

What is the severity of CVE-2025-39773?

CVE-2025-39773 is considered a medium severity vulnerability due to potential local disruption in the Linux kernel.

How do I fix CVE-2025-39773?

To fix CVE-2025-39773, update your Linux kernel to a version that includes the patch for this vulnerability.

What does CVE-2025-39773 affect?

CVE-2025-39773 affects the Linux kernel version 6.16.0 and later implementations that use the bridge multicast query features.

What are the potential consequences of CVE-2025-39773?

The potential consequences of CVE-2025-39773 include a local system lockup when handling multicast queries under specific conditions.

In which Linux kernel functions does CVE-2025-39773 manifest?

CVE-2025-39773 manifests in the br_multicast_query_expired() and br_multicast_send_query() functions within the kernel networking code.

CVE-2025-39773: net: bridge: fix soft lockup in br_multicast_query_expired()

Affected Software

Remediation

Event History

Parent advisories

Peer vulnerabilities

Frequently Asked Questions

What is the severity of CVE-2025-39773?

How do I fix CVE-2025-39773?

What does CVE-2025-39773 affect?

What are the potential consequences of CVE-2025-39773?

In which Linux kernel functions does CVE-2025-39773 manifest?

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Resources

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