CVE-2025-39980
BaseFortify
Publication date: 2025-10-15
Last updated on: 2025-10-16
Assigner: kernel.org
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | 6.17.0-rc6 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability in the Linux kernel involves improper handling of nexthop groups with FDB (Forwarding Database) status changes. The kernel previously allowed changing the FDB status of a nexthop while it was part of a group, which is invalid and can cause a kernel NULL pointer dereference (crash). Specifically, the kernel did not forbid changing a nexthop from FDB to non-FDB or vice versa when the nexthop was in a group, leading to an invalid configuration and potential system crash. The fix prevents changing the FDB status of a nexthop while it is in a group, ensuring stable and valid nexthop group configurations.
How can this vulnerability impact me? :
This vulnerability can cause a kernel crash (NULL pointer dereference) when invalid nexthop group configurations occur due to improper FDB status changes. Such crashes can lead to system instability, denial of service, and potential disruption of network routing functionality on affected Linux systems.
How can this vulnerability be detected on my network or system? Can you suggest some commands?
You can detect this vulnerability by checking for invalid nexthop configurations involving FDB and non-FDB nexthop groups. Use the following commands to inspect nexthop configurations and test for errors: # ip nexthop add id 1 via 192.0.2.1 fdb # ip nexthop add id 2 group 1 If you get an error like 'Non FDB nexthop group cannot have fdb nexthops', it indicates the kernel is enforcing the fix. Also, try replacing nexthop FDB status while in a group: # ip nexthop add id 7 via 192.0.2.2 dev dummy1 # ip nexthop add id 8 group 7 # ip nexthop replace id 7 via 192.0.2.2 fdb If you get an error 'Cannot change nexthop FDB status while in a group', the fix is applied. Otherwise, the system may be vulnerable. Additionally, look for kernel oops or NULL pointer dereference logs related to fib_lookup_good_nhc or ping failures to IPs routed via nexthop groups.
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability immediately, ensure that your Linux kernel is updated to a version that includes the fix preventing nexthop FDB status changes while the nexthop is in a group. Avoid creating or modifying nexthop groups that mix FDB and non-FDB nexthops. Specifically, do not perform 'ip nexthop replace' commands that change FDB status on nexthops already in groups. Monitor and correct any invalid nexthop configurations to prevent kernel NULL pointer dereferences and system crashes.