CVE-2026-89790 (GCVE-0-2026-89790)

Vulnerability from cvelistv5 – Published: 2026-09-16 08:48 – Updated: 2026-10-19 08:52
VLAI
Title
ipv6: avoid divide by zero in rt6_multipath_rebalance
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: avoid divide by zero in rt6_multipath_rebalance rt6_multipath_rebalance() calculates the total eligible nexthop weight in one pass and programs upper bounds in a second pass. Since RTM_NEWROUTE is RTNL-free, a concurrent ignore_routes_with_linkdown update can make the first pass return zero while the second sees an eligible nexthop, causing rt6_upper_bound_set() to divide by zero. UBSAN: division-overflow in net/ipv6/route.c:4845:17 Oops: divide error: 0000 [#1] SMP KASAN NOPTI rt6_upper_bound_set() net/ipv6/route.c:4845 rt6_multipath_rebalance() fib6_add_rt2node() ip6_route_multipath_add() inet6_rtm_newroute() Skip upper-bound calculation when the first pass reports a zero total. This respects the lock-free performance considerations here and solves insecure scenarios.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6639 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: bd11ff421d36abdb585b9104fa70057bf01b3110 , < f30cf8fd9872299c0c27f9916252ba2b9f422dce (git)
Affected: bd11ff421d36abdb585b9104fa70057bf01b3110 , < f82b5dbb2fef65b52a62d5ffe05e0483c4385a83 (git)
Affected: bd11ff421d36abdb585b9104fa70057bf01b3110 , < d2c26c2911dd1a363c488add4fb63eb5f0f28f87 (git)
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Linux Linux Affected: 6.16
Unaffected: 0 , < 6.16 (semver)
Unaffected: 6.18.52 , ≤ 6.18.* (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "net/ipv6/route.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: avoid divide by zero in rt6_multipath_rebalance\n\nrt6_multipath_rebalance() calculates the total eligible nexthop weight\nin one pass and programs upper bounds in a second pass. Since\nRTM_NEWROUTE is RTNL-free, a concurrent\nignore_routes_with_linkdown update can make the first pass return zero\nwhile the second sees an eligible nexthop, causing\nrt6_upper_bound_set() to divide by zero.\n\nUBSAN: division-overflow in net/ipv6/route.c:4845:17\nOops: divide error: 0000 [#1] SMP KASAN NOPTI\n  rt6_upper_bound_set() net/ipv6/route.c:4845\n  rt6_multipath_rebalance()\n  fib6_add_rt2node()\n  ip6_route_multipath_add()\n  inet6_rtm_newroute()\n\nSkip upper-bound calculation when the first pass reports a zero total.\nThis respects the lock-free performance considerations here and solves\ninsecure scenarios."
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      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:52:44.129Z",
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    "datePublished": "2026-09-16T08:48:26.343Z",
    "dateReserved": "2026-09-11T19:38:34.766Z",
    "dateUpdated": "2026-10-19T08:52:44.129Z",
    "state": "PUBLISHED"
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: avoid divide by zero in rt6_multipath_rebalance\n\nrt6_multipath_rebalance() calculates the total eligible nexthop weight\nin one pass and programs upper bounds in a second pass. Since\nRTM_NEWROUTE is RTNL-free, a concurrent\nignore_routes_with_linkdown update can make the first pass return zero\nwhile the second sees an eligible nexthop, causing\nrt6_upper_bound_set() to divide by zero.\n\nUBSAN: division-overflow in net/ipv6/route.c:4845:17\nOops: divide error: 0000 [#1] SMP KASAN NOPTI\n  rt6_upper_bound_set() net/ipv6/route.c:4845\n  rt6_multipath_rebalance()\n  fib6_add_rt2node()\n  ip6_route_multipath_add()\n  inet6_rtm_newroute()\n\nSkip upper-bound calculation when the first pass reports a zero total.\nThis respects the lock-free performance considerations here and solves\ninsecure scenarios."
          }
        ],
        "id": "CVE-2026-89790",
        "lastModified": "2026-10-19T09:18:22.690",
        "metrics": {},
        "published": "2026-09-16T09:17:09.827",
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      "title": "kernel: ipv6: avoid divide by zero in rt6_multipath_rebalance",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89790.json",
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}



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