{"id":"CVE-2026-89790","published":"2026-09-16T09:17:09.827","lastModified":"2026-09-16T09:17:09.827","description":"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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/d2c26c2911dd1a363c488add4fb63eb5f0f28f87","tags":[]},{"url":"https://git.kernel.org/stable/c/f30cf8fd9872299c0c27f9916252ba2b9f422dce","tags":[]},{"url":"https://git.kernel.org/stable/c/f82b5dbb2fef65b52a62d5ffe05e0483c4385a83","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}