CVE-2026-89790
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.
Affected versions
Linux kernel versions
6.16
and later are affected. Fixed in
6.18.52,
7.2.6,
7.3-rc1
and their respective stable series.
References
3 totalFrequently asked questions
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What is CVE-2026-89790?
CVE-2026-89790 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 6.16 onward and has been patched in 6.18.52, 7.2.6 and 7.3-rc1. CVE-2026-89790 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-89790?
Yes. CVE-2026-89790 has been patched. Fixed versions include 6.18.52, 7.2.6 and 7.3-rc1. If you are running Linux kernel 6.16 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-89790 actively exploited?
No. CVE-2026-89790 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.