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
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-39773
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-39773
Patch
https://git.kernel.org/stable/c/34171b9e53bd1dc264f5556579f2b04f04435c73
Patch
https://git.kernel.org/stable/c/43e281fde5e76a866a4d10780c35023f16c0e432
Patch
https://git.kernel.org/stable/c/5bf5fce8a0c2a70d063af778fdb5b27238174cdd
Patch
https://git.kernel.org/stable/c/96476b043efb86a94f2badd260f7f99c97bd5893
Patch
https://git.kernel.org/stable/c/bdb19cd0de739870bb3494c815138b9dc30875c4
Patch
https://git.kernel.org/stable/c/d1547bf460baec718b3398365f8de33d25c5f36f
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