CVE-2026-46099

/// Technical description

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

net: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels

seg6_input_core() and rpl_input() call ip6_route_input() which sets a

NOREF dst on the skb, then pass it to dst_cache_set_ip6() invoking

dst_hold() unconditionally.

On PREEMPT_RT, ksoftirqd is preemptible and a higher-priority task can

release the underlying pcpu_rt between the lookup and the caching

through a concurrent FIB lookup on a shared nexthop.

Simplified race sequence:

ksoftirqd/X higher-prio task (same CPU X)

----------- --------------------------------

seg6_input_core(,skb)/rpl_input(skb)

dst_cache_get()

-> miss

ip6_route_input(skb)

-> ip6_pol_route(,skb,flags)

[RT6_LOOKUP_F_DST_NOREF in flags]

-> FIB lookup resolves fib6_nh

[nhid=N route]

-> rt6_make_pcpu_route()

[creates pcpu_rt, refcount=1]

pcpu_rt->sernum = fib6_sernum

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References