{"id":"CVE-2026-46099","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-46099","generatedAt":"2026-10-28T05:59:11.583Z","title":"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()…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels\n\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:\n\n ksoftirqd/X higher-prio task (same CPU X)\n ----------- --------------------------------\n seg6_input_core(,skb)/rpl_input(skb)\n dst_cache_get()\n -> miss\n ip6_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]\n pcpu_rt->sernum = fib6_sernum\n [fib6_sernum=W]\n -> cmpxchg(fib6_nh.rt6i_pcpu,\n NULL, pcpu_rt)\n [slot was empty, store succeeds]\n -> skb_dst_set_noref(skb, dst)\n [dst is pcpu_rt, refcount still 1]\n\n rt_genid_bump_ipv6()\n -> bumps fib6_sernum\n [fib6_sernum from W to Z]\n ip6_route_output()\n -> ip6_pol_route()\n -> FIB lookup resolves fib6_nh\n [nhid=N]\n -> rt6_get_pcpu_route()\n pcpu_rt->sernum != fib6_sernum\n [W <> Z, stale]\n -> prev = xchg(rt6i_pcpu, NULL)\n -> dst_release(prev)\n [prev is pcpu_rt,\n refcount 1->0, dead]\n\n dst = skb_dst(skb)\n [dst is the dead pcpu_rt]\n dst_cache_set_ip6(dst)\n -> dst_hold() on dead dst\n -> WARN / use-after-free\n\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.\n\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.","published":"2026-05-27T14:17:32.000Z","lastModified":"2026-10-19T20:18:29.000Z","status":"Modified","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-416","CWE-911"],"affected":["linux/linux kernel"],"epss":{"score":0.00288,"percentile":0.21285,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.29%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/51fef5a7c4d160839199e941929456ba21ddf73c","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/52f9db67f8f35f436366cf4980b4f0a2583d0ef0","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6bd17925bd6866027a6555db17905b9fc073d38d","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9dd5481f960e337b81d7dfe429529495c1c481c0","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b258b849a580285a1692e782ebc902b44c884a71","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b778b6d095421619c331fd2d7751143cd5387103","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f9c52a6ba9780bd27e0bf4c044fd91c13c778b6e","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://access.redhat.com/errata/RHSA-2026:45114","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:59662","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:59663","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:62568","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:64767","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:65712","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/security/cve/CVE-2026-46099","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2481972","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-784472.html","source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46099.json","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-46099","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}