CVE-2026-43374

In the Linux kernel, the following vulnerability has been resolved:

net: nexthop: fix percpu use-after-free in remove_nh_grp_entry

When removing a nexthop from a group, remove_nh_grp_entry() publishes the new group via rcu_assign_pointer() then immediately frees the removed entrys percpu stats with free_percpu(). However, the synchronize_net() grace period in the caller remove_nexthop_from_groups() runs after the free. RCU readers that entered before the publish still see the old group and can dereference the freed stats via nh_grp_entry_stats_inc() -> get_cpu_ptr(nhge->stats), causing a use-after-free on percpu memory.

Fix by deferring the free_percpu() until after synchronize_net() in the caller. Removed entries are chained via nh_list onto a local deferred free list. After the grace period completes and all RCU readers have finished, the percpu stats are safely freed.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/9e08ad731862b22a87cc55f752e16d66cdc9e231
• https://git.kernel.org/stable/c/ab5ebab9664214ba41a7633cb4e72f128204f924
• https://git.kernel.org/stable/c/abf4feaee6405f1441929c6ebe7a250f2cd170a7
• https://git.kernel.org/stable/c/b2662e7593e94ae09b1cf7ee5f09160a3612bcb2