Medium severity · published Sep 11, 2025
CVE-2025-39773
net: bridge: fix soft lockup in br_multicast_query_expired()
5.5
CVSS
0.1%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 2% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
2.6.34 before 5.15.190; 5.16 before 6.1.149; 6.2 before 6.6.103; 6.7 before 6.12.44; 6.13 before 6.16.4; 6.17; +1 more · source: NVD
LI
Linux · Linux
d902eee43f1951b358d7347d9165c6af21cf7b1b before 34171b9e53bd1dc264f5556579f2b04f04435c73; d902eee43f1951b358d7347d9165c6af21cf7b1b before 43e281fde5e76a866a4d10780c35023f16c0e432; d902eee43f1951b358d7347d9165c6af21cf7b1b before 96476b043efb86a94f2badd260f7f99c97bd5893; d902eee43f1951b358d7347d9165c6af21cf7b1b before bdb19cd0de739870bb3494c815138b9dc30875c4; d902eee43f1951b358d7347d9165c6af21cf7b1b before 5bf5fce8a0c2a70d063af778fdb5b27238174cdd; d902eee43f1951b358d7347d9165c6af21cf7b1b before d1547bf460baec718b3398365f8de33d25c5f36f; +1 more · source: vendor
DL
Debian Linux · Debian
11.0 · source: NVD
SC
SIMATIC CN 4100 · Siemens
before V5.0 · source: CISA
SS
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.5; V3.1.6; V3.1.7; V3.1.5; V3.1.6; V3.1.7 · source: CISA
SS
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP · Siemens
V3.1.5; V3.1.6; V3.1.7; V3.1.5; V3.1.6; V3.1.7 · source: CISA
SS
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.5; V3.1.6; V3.1.7 · source: CISA