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CVE-2025-39773

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 smallerthan jiffies, the timer will expire immediately, and then call mod_timer()again, which creates a loop and may trigger the following soft lockupissue. 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: __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 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 upThe multicast_startup_query_interval can also cause this issue. Similar tothe commit 99b40610956a ("net: bridge: mcast: add and enforce queryinterval minimum"), add check for the query interval maximum to fix thisissue.

CVE-2025-39773

Description

POC

Reference

Github