CVE-2026-46099
net: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels
- Published
- Updated
- Reserved
- Assigned by
- Linux
Description
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High8.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| redhat-SADPADP (enrichment) | 3.1 | High7.3 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H |
| NVDNVD · Modified | 3.1 | High8.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.29% · top 78% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.1.
Weakness
Affected products
- affected af4a2209b1344939eaac11f269c261d347cbc3ee – < 51fef5a7c4d160839199e941929456ba21ddf73c
- affected af4a2209b1344939eaac11f269c261d347cbc3ee – < b258b849a580285a1692e782ebc902b44c884a71
- affected af4a2209b1344939eaac11f269c261d347cbc3ee – < 6bd17925bd6866027a6555db17905b9fc073d38d
- affected af4a2209b1344939eaac11f269c261d347cbc3ee – < 52f9db67f8f35f436366cf4980b4f0a2583d0ef0
- affected af4a2209b1344939eaac11f269c261d347cbc3ee – < b778b6d095421619c331fd2d7751143cd5387103
- affected af4a2209b1344939eaac11f269c261d347cbc3ee – < 9dd5481f960e337b81d7dfe429529495c1c481c0
- affected af4a2209b1344939eaac11f269c261d347cbc3ee – < f9c52a6ba9780bd27e0bf4c044fd91c13c778b6e
- affected 4.12
- unaffected < 4.12
- unaffected 5.15.209 – ≤ 5.15.*
- unaffected 6.1.175 – ≤ 6.1.*
- unaffected 6.6.140 – ≤ 6.6.*
- unaffected 6.12.86 – ≤ 6.12.*
- unaffected 6.18.27 – ≤ 6.18.*
- unaffected 7.0.4 – ≤ 7.0.*
- unaffected 7.1 – ≤ *
References (17)
- https://git.kernel.org/stable/c/51fef5a7c4d160839199e941929456ba21ddf73c (opens in a new tab)
- https://git.kernel.org/stable/c/b258b849a580285a1692e782ebc902b44c884a71 (opens in a new tab)
- https://git.kernel.org/stable/c/6bd17925bd6866027a6555db17905b9fc073d38d (opens in a new tab)
- https://git.kernel.org/stable/c/52f9db67f8f35f436366cf4980b4f0a2583d0ef0 (opens in a new tab)
- https://git.kernel.org/stable/c/b778b6d095421619c331fd2d7751143cd5387103 (opens in a new tab)
- https://git.kernel.org/stable/c/9dd5481f960e337b81d7dfe429529495c1c481c0 (opens in a new tab)
- https://git.kernel.org/stable/c/f9c52a6ba9780bd27e0bf4c044fd91c13c778b6e (opens in a new tab)
- https://access.redhat.com/security/cve/CVE-2026-46099 (opens in a new tab)vdb-entryx_refsource_REDHAT
- RHBZ#2481972 (opens in a new tab)issue-trackingx_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46099.json (opens in a new tab)x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:64767 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:45114 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:59662 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:65712 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:62568 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:59663 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
- https://cert-portal.siemens.com/productcert/html/ssa-784472.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://trackcve.app/cve/CVE-2026-46099)Record last updated .