net: nexthop: fix percpu use-after-free in remove_nh_grp_entry (CVE-2026-43374) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-43374

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

Answer in brief

CVE-2026-43374 records a Unknown severity vulnerability in net: nexthop: fix percpu use-after-free in remove_nh_grp_entry. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published May 8, 2026Updated Aug 5, 2026Source checked Sep 19, 2026First seen by HOL Aug 5, 2026Material review Aug 5, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=f4676ea74b8549cd88dbfe2a592ce4530039e61f <abf4feaee6405f1441929c6ebe7a250f2cd170a7 \|\| >=f4676ea74b8549cd88dbfe2a592ce4530039e61f <ab5ebab9664214ba41a7633cb4e72f128204f924 \|\| >=f4676ea74b8549cd88dbfe2a592ce4530039e61f <9e08ad731862b22a87cc55f752e16d66cdc9e231 \|\| >=f4676ea74b8549cd88dbfe2a592ce4530039e61f <b2662e7593e94ae09b1cf7ee5f09160a3612bcb2	abf4feaee6405f1441929c6ebe7a250f2cd170a7, ab5ebab9664214ba41a7633cb4e72f128204f924, 9e08ad731862b22a87cc55f752e16d66cdc9e231, b2662e7593e94ae09b1cf7ee5f09160a3612bcb2
Linux/Linuxgeneric	6.9	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to abf4feaee6405f1441929c6ebe7a250f2cd170a7 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
May 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 5, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.