CVE-2026-46099

Debolezza

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 [fib6_sernum=W] -> cmpxchg(fib6_nh.rt6i_pcpu, NULL, pcpu_rt) [slot was empty, store succeeds] -> skb_dst_set_noref(skb, dst) [dst is pcpu_rt, refcount still 1] rt_genid_bump_ipv6() -> bumps fib6_sernum [fib6_sernum from W to Z] ip6_route_output() -> ip6_pol_route() -> FIB lookup resolves fib6_nh [nhid=N] -> rt6_get_pcpu_route() pcp

Prodotti interessati

• linux linux_kernel

Riferimenti

• https://git.kernel.org/stable/c/51fef5a7c4d160839199e941929456ba21ddf73c
• https://git.kernel.org/stable/c/52f9db67f8f35f436366cf4980b4f0a2583d0ef0
• https://git.kernel.org/stable/c/6bd17925bd6866027a6555db17905b9fc073d38d
• https://git.kernel.org/stable/c/9dd5481f960e337b81d7dfe429529495c1c481c0
• https://git.kernel.org/stable/c/b258b849a580285a1692e782ebc902b44c884a71
• https://git.kernel.org/stable/c/b778b6d095421619c331fd2d7751143cd5387103