{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-46099","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-05-13T15:03:33.097Z","datePublished":"2026-05-27T12:59:04.628Z","dateUpdated":"2026-08-26T12:04:58.201Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:29:36.501Z"},"descriptions":[{"lang":"en","value":"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."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The seg6/RPL lwtunnel input handlers run on the IPv6 packet receive/forward path (lwtunnel_input → seg6_input/rpl_input); a remote attacker sending IPv6 packets matching a configured SRv6/RPL-encap route reaches the vulnerable code.\nAC:H - The UAF manifests only on PREEMPT_RT kernels built without PREEMPT_RT_NEEDS_BH_LOCK (a rare, non-default configuration) and additionally requires winning a tight race against a higher-priority task's concurrent FIB lookup plus a sernum bump on a shared nexthop — conditions outside the attacker's control.\nPR:N - The triggering packets require no privileges; the SRv6/RPL route configuration is an environmental precondition (CAP_NET_ADMIN to set up), not a privilege the network attacker must hold.\nUI:N - The bug is triggered purely by inbound packet processing in softirq context; no victim interaction is needed.\nS:U - The use-after-free is confined to kernel route/dst objects within the kernel's own security authority; no boundary (VM/IOMMU) is crossed.\nC:H - The freed rt6_info/dst object is read back (rt6_get_cookie/dst dereferences) and can be reallocated with attacker-influenced heap content, enabling kernel memory disclosure.\nI:H - A use-after-free on a route object allows heap-spray reallocation and write/control primitives via the dangling dst that is subsequently used for routing decisions.\nA:H - dst_hold() on the dead object triggers a WARN and the use-after-free of a freed route can cause an oops/panic, crashing the kernel."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/rpl_iptunnel.c","net/ipv6/seg6_iptunnel.c"],"versions":[{"version":"af4a2209b1344939eaac11f269c261d347cbc3ee","lessThan":"51fef5a7c4d160839199e941929456ba21ddf73c","status":"affected","versionType":"git"},{"version":"af4a2209b1344939eaac11f269c261d347cbc3ee","lessThan":"b258b849a580285a1692e782ebc902b44c884a71","status":"affected","versionType":"git"},{"version":"af4a2209b1344939eaac11f269c261d347cbc3ee","lessThan":"6bd17925bd6866027a6555db17905b9fc073d38d","status":"affected","versionType":"git"},{"version":"af4a2209b1344939eaac11f269c261d347cbc3ee","lessThan":"52f9db67f8f35f436366cf4980b4f0a2583d0ef0","status":"affected","versionType":"git"},{"version":"af4a2209b1344939eaac11f269c261d347cbc3ee","lessThan":"b778b6d095421619c331fd2d7751143cd5387103","status":"affected","versionType":"git"},{"version":"af4a2209b1344939eaac11f269c261d347cbc3ee","lessThan":"9dd5481f960e337b81d7dfe429529495c1c481c0","status":"affected","versionType":"git"},{"version":"af4a2209b1344939eaac11f269c261d347cbc3ee","lessThan":"f9c52a6ba9780bd27e0bf4c044fd91c13c778b6e","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/rpl_iptunnel.c","net/ipv6/seg6_iptunnel.c"],"versions":[{"version":"4.12","status":"affected"},{"version":"0","lessThan":"4.12","status":"unaffected","versionType":"semver"},{"version":"5.15.209","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.175","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.140","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.86","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.27","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.0.4","lessThanOrEqual":"7.0.*","status":"unaffected","versionType":"semver"},{"version":"7.1","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"5.15.209"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.1.175"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.6.140"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.12.86"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.18.27"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"7.0.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"7.1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/51fef5a7c4d160839199e941929456ba21ddf73c"},{"url":"https://git.kernel.org/stable/c/b258b849a580285a1692e782ebc902b44c884a71"},{"url":"https://git.kernel.org/stable/c/6bd17925bd6866027a6555db17905b9fc073d38d"},{"url":"https://git.kernel.org/stable/c/52f9db67f8f35f436366cf4980b4f0a2583d0ef0"},{"url":"https://git.kernel.org/stable/c/b778b6d095421619c331fd2d7751143cd5387103"},{"url":"https://git.kernel.org/stable/c/9dd5481f960e337b81d7dfe429529495c1c481c0"},{"url":"https://git.kernel.org/stable/c/f9c52a6ba9780bd27e0bf4c044fd91c13c778b6e"}],"title":"net: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"affected":[{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:10.2"],"defaultStatus":"affected","packageName":"kernel","product":"Red Hat Enterprise Linux 10","vendor":"Red Hat","versions":[{"lessThan":"*","status":"unaffected","version":"0:6.12.0-211.39.1.el10_2","versionType":"rpm"}]},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:rhel_e4s:9.2"],"defaultStatus":"affected","packageName":"kernel","product":"Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions","vendor":"Red Hat","versions":[{"lessThan":"*","status":"unaffected","version":"0:5.14.0-284.188.1.el9_2","versionType":"rpm"}]},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:rhel_e4s:9.2::nfv"],"defaultStatus":"affected","packageName":"kernel-rt","product":"Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions","vendor":"Red Hat","versions":[{"lessThan":"*","status":"unaffected","version":"0:5.14.0-284.188.1.rt14.473.el9_2","versionType":"rpm"}]},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:6"],"defaultStatus":"unaffected","packageName":"kernel","product":"Red Hat Enterprise Linux 6","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:7"],"defaultStatus":"unaffected","packageName":"kernel","product":"Red Hat Enterprise Linux 7","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:7"],"defaultStatus":"unaffected","packageName":"kernel-rt","product":"Red Hat Enterprise Linux 7","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:8"],"defaultStatus":"unaffected","packageName":"kernel","product":"Red Hat Enterprise Linux 8","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:8"],"defaultStatus":"unaffected","packageName":"kernel-rt","product":"Red Hat Enterprise Linux 8","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"],"defaultStatus":"affected","packageName":"kernel","product":"Red Hat Enterprise Linux 9","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"],"defaultStatus":"affected","packageName":"kernel-rt","product":"Red Hat Enterprise Linux 9","vendor":"Red Hat"}],"datePublic":"2026-05-27T00:00:00.000Z","descriptions":[{"lang":"en","value":"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."}],"metrics":[{"other":{"content":{"namespace":"https://access.redhat.com/security/updates/classification/","value":"Important"},"type":"Red Hat severity rating"}},{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":7.3,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-911","description":"Improper Update of Reference Count","lang":"en","type":"CWE"}]}],"references":[{"tags":["vdb-entry","x_refsource_REDHAT"],"url":"https://access.redhat.com/security/cve/CVE-2026-46099"},{"name":"RHBZ#2481972","tags":["issue-tracking","x_refsource_REDHAT"],"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2481972"},{"tags":["x_sadp-csaf-vex"],"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46099.json"},{"tags":["vendor-advisory","x_refsource_REDHAT"],"url":"https://access.redhat.com/errata/RHSA-2026:45114"},{"tags":["vendor-advisory","x_refsource_REDHAT"],"url":"https://access.redhat.com/errata/RHSA-2026:59662"},{"tags":["vendor-advisory","x_refsource_REDHAT"],"url":"https://access.redhat.com/errata/RHSA-2026:59663"}],"solutions":[{"lang":"en","value":"RHSA-2026:45114: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10)"},{"lang":"en","value":"RHSA-2026:59662: Red Hat Enterprise Linux AppStream E4S (v.9.2), Red Hat Enterprise Linux BaseOS E4S (v.9.2)"},{"lang":"en","value":"RHSA-2026:59663: Red Hat Enterprise Linux Real Time E4S (v.9.2), Red Hat Enterprise Linux Real Time for NFV E4S (v.9.2)"}],"timeline":[{"lang":"en","time":"2026-05-27T00:00:00.000Z","value":"Reported to Red Hat."},{"lang":"en","time":"2026-05-27T00:00:00.000Z","value":"Made public."}],"title":"kernel: net: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels","x_adpType":"supplier","x_generator":{"engine":"sadp-cli 1.0.0"},"providerMetadata":{"orgId":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c","shortName":"redhat-SADP","dateUpdated":"2026-08-26T12:04:58.201Z"}}]}}