CVE-2025-39773
BaseFortify
Publication date: 2025-09-11
Last updated on: 2025-11-03
Assigner: kernel.org
Description
Description
CVSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | 6.1.153-1 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is a soft lockup issue in the Linux kernel's network bridge code. When the multicast_query_interval is set to a very large value, a local variable 'time' in the function br_multicast_send_query() can overflow. This causes the timer to expire immediately and repeatedly call mod_timer(), creating a loop that leads to a CPU soft lockup, where the CPU becomes stuck and unresponsive for an extended period.
How can this vulnerability impact me? :
The vulnerability can cause a CPU soft lockup, meaning the affected CPU core can become stuck and unresponsive for a long time. This can degrade system performance, cause network disruptions, and potentially lead to denial of service conditions on systems using the Linux kernel's bridge functionality with multicast enabled.
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability can be detected by checking for soft lockup warnings related to the bridge multicast query timer in the system logs, such as messages like 'watchdog: BUG: soft lockup - CPU#1 stuck for ...'. Additionally, you can attempt to reproduce the issue by creating a bridge interface and setting the multicast_query_interval to a very large value using the following commands: 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 If the system experiences a soft lockup or similar issues after these commands, the vulnerability is present.
What immediate steps should I take to mitigate this vulnerability?
Immediate mitigation steps include avoiding setting the multicast_query_interval and multicast_startup_query_interval to excessively large values that could cause the timer overflow and soft lockup. Ensure that your Linux kernel is updated to a version where this vulnerability is fixed, as the issue was resolved by adding checks for maximum query interval values to prevent overflow and soft lockups.