CVE-2026-43374: net: nexthop: fix percpu use-after-free in remove_nh_grp_entry

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-08 · updated 2026-10-19
Weakness: CWE-416

Description

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 entry's 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.

Affected products

Linux kernel: from 6.9 before 6.12.78; from 6.13 before 6.18.19; from 6.19 before 6.19.9; 6.9, 7.0-rc1, 7.0-rc2, 7.0-rc3 — fixed in 6.12.78, 6.18.19, 6.19.9

How to fix

Upgrade to a fixed version: Linux kernel 6.12.78, 6.18.19, 6.19.9. Check the vendor advisory for mitigations.

References

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