{
  "threat_severity" : "Important",
  "public_date" : "2026-05-27T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: net: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels",
    "id" : "2481972",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2481972"
  },
  "cvss3" : {
    "cvss3_base_score" : "7.0",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
    "status" : "draft"
  },
  "cwe" : "CWE-911",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nnet: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels\nseg6_input_core() and rpl_input() call ip6_route_input() which sets a\nNOREF dst on the skb, then pass it to dst_cache_set_ip6() invoking\ndst_hold() unconditionally.\nOn PREEMPT_RT, ksoftirqd is preemptible and a higher-priority task can\nrelease the underlying pcpu_rt between the lookup and the caching\nthrough a concurrent FIB lookup on a shared nexthop.\nSimplified race sequence:\nksoftirqd/X                       higher-prio task (same CPU X)\n-----------                       --------------------------------\nseg6_input_core(,skb)/rpl_input(skb)\ndst_cache_get()\n-> miss\nip6_route_input(skb)\n-> ip6_pol_route(,skb,flags)\n[RT6_LOOKUP_F_DST_NOREF in flags]\n-> FIB lookup resolves fib6_nh\n[nhid=N route]\n-> rt6_make_pcpu_route()\n[creates pcpu_rt, refcount=1]\npcpu_rt->sernum = fib6_sernum\n[fib6_sernum=W]\n-> cmpxchg(fib6_nh.rt6i_pcpu,\nNULL, pcpu_rt)\n[slot was empty, store succeeds]\n-> skb_dst_set_noref(skb, dst)\n[dst is pcpu_rt, refcount still 1]\nrt_genid_bump_ipv6()\n-> bumps fib6_sernum\n[fib6_sernum from W to Z]\nip6_route_output()\n-> ip6_pol_route()\n-> FIB lookup resolves fib6_nh\n[nhid=N]\n-> rt6_get_pcpu_route()\npcpu_rt->sernum != fib6_sernum\n[W <> Z, stale]\n-> prev = xchg(rt6i_pcpu, NULL)\n-> dst_release(prev)\n[prev is pcpu_rt,\nrefcount 1->0, dead]\ndst = skb_dst(skb)\n[dst is the dead pcpu_rt]\ndst_cache_set_ip6(dst)\n-> dst_hold() on dead dst\n-> WARN / use-after-free\nFor the race to occur, ksoftirqd must be preemptible (PREEMPT_RT without\nPREEMPT_RT_NEEDS_BH_LOCK) and a concurrent task must be able to release\nthe pcpu_rt. Shared nexthop objects provide such a path, as two routes\npointing to the same nhid share the same fib6_nh and its rt6i_pcpu\nentry.\nFix seg6_input_core() and rpl_input() by calling skb_dst_force() after\nip6_route_input() to force the NOREF dst into a refcounted one before\ncaching.\nThe output path is not affected as ip6_route_output() already returns a\nrefcounted dst.", "A flaw was found in the Linux kernel's IPv6 networking implementation, specifically within the `seg6` and `rpl` lwtunnels. A race condition can occur when handling destination cache entries, where a `NOREF` (no reference) destination object is used after it has been freed. This use-after-free vulnerability can lead to system instability or a denial of service (DoS) on systems configured with `PREEMPT_RT` (Preemptible Real-Time) kernel." ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-46099\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-46099\nhttps://lore.kernel.org/linux-cve-announce/2026052704-CVE-2026-46099-2a55@gregkh/T" ],
  "name" : "CVE-2026-46099",
  "csaw" : false
}