--- id: CVE-2026-46099 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_… summary: |- 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_… severity: high cvss: 8.1 cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-911 vendor: linux product: linux_kernel affected: - 'linux_kernel >= 4.12, < 5.15.209' - 'linux_kernel >= 5.16, < 6.1.175' - 'linux_kernel >= 6.2, < 6.6.140' - 'linux_kernel >= 6.7, < 6.12.86' - 'linux_kernel >= 6.13, < 6.18.27' - 'linux_kernel >= 6.19, < 7.0.4' - linux_kernel = 7.1 patched: - linux_kernel 7.0.4 published: '2026-05-27' updated: '2026-09-09' sourceUpdated: '2026-09-09T13:20:15.450' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-46099' references: - url: 'https://git.kernel.org/stable/c/51fef5a7c4d160839199e941929456ba21ddf73c' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/52f9db67f8f35f436366cf4980b4f0a2583d0ef0' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/6bd17925bd6866027a6555db17905b9fc073d38d' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/9dd5481f960e337b81d7dfe429529495c1c481c0' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/b258b849a580285a1692e782ebc902b44c884a71' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/b778b6d095421619c331fd2d7751143cd5387103' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/f9c52a6ba9780bd27e0bf4c044fd91c13c778b6e' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://access.redhat.com/errata/RHSA-2026:45114' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:59662' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:59663' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:62568' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:64767' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:65712' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/security/cve/CVE-2026-46099' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2481972' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46099.json label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://www.cve.org/CVERecord?id=CVE-2026-46099' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-46099' - url: >- https://lore.kernel.org/linux-cve-announce/2026052704-CVE-2026-46099-2a55@gregkh/T tags: - nvd - cve.org - csaf - vex - red-hat epss: 0.00288 epssPercentile: 0.21691 scores: nvd: 8.1 vendor: 7.3 cna: 8.1 ingestedAt: '2026-07-27T14:19:54.563Z' --- ## Overview 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() pcpu_rt->sernum != fib6_sernum [W <> Z, stale] -> prev = xchg(rt6i_pcpu, NULL) -> dst_release(prev) [prev is pcpu_rt, refcount 1->0, dead] dst = skb_dst(skb) [dst is the dead pcpu_rt] dst_cache_set_ip6(dst) -> dst_hold() on dead dst -> WARN / use-after-free For the race to occur, ksoftirqd must be preemptible (PREEMPT_RT without PREEMPT_RT_NEEDS_BH_LOCK) and a concurrent task must be able to release the pcpu_rt. Shared nexthop objects provide such a path, as two routes pointing to the same nhid share the same fib6_nh and its rt6i_pcpu entry. Fix seg6_input_core() and rpl_input() by calling skb_dst_force() after ip6_route_input() to force the NOREF dst into a refcounted one before caching. The output path is not affected as ip6_route_output() already returns a refcounted dst. ## Affected - `linux_kernel >= 4.12, < 5.15.209` - `linux_kernel >= 5.16, < 6.1.175` - `linux_kernel >= 6.2, < 6.6.140` - `linux_kernel >= 6.7, < 6.12.86` - `linux_kernel >= 6.13, < 6.18.27` - `linux_kernel >= 6.19, < 7.0.4` - `linux_kernel = 7.1` ## Remediation Upgrade past the affected range: - `linux_kernel 7.0.4` ## Vendor advisories - **RHSA-2026:64767** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux BaseOS EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0), Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0), Red Hat Enterprise Linux Real Time EUS (v. 10.0) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64767) - **RHSA-2026:45114** · Red Hat · fixed in: 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 for NFV (v. 10), Red Hat Enterprise Linux Real Time (v. 10) · released 2026-07-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:45114) - **RHSA-2026:59662** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.2), Red Hat Enterprise Linux BaseOS E4S (v.9.2) · released 2026-08-26 · [advisory](https://access.redhat.com/errata/RHSA-2026:59662) - **RHSA-2026:62568** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat Enterprise Linux BaseOS EUS (v.9.6), Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6), Red Hat Enterprise Linux Real Time EUS (v.9.6) · released 2026-09-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:62568) - **RHSA-2026:59663** · Red Hat · fixed in: Red Hat Enterprise Linux Real Time for NFV E4S (v.9.2), Red Hat Enterprise Linux Real Time E4S (v.9.2) · released 2026-08-26 · [advisory](https://access.redhat.com/errata/RHSA-2026:59663) - **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 9 · updated 2026-09-09 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46099.json) - **RHSA-2026:65712** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.4), Red Hat Enterprise Linux BaseOS E4S (v.9.4), Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4), Red Hat Enterprise Linux Real Time E4S (v.9.4) · released 2026-09-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:65712)