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.
Metrics
Affected Vendors & Products
| Vendors | Products |
|---|---|
| Linux |
|
No data.
No data.
References
History
Sun, 20 Sep 2026 06:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-368 |
Fri, 18 Sep 2026 12:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-369 |
Wed, 16 Sep 2026 14:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-369 |
Wed, 16 Sep 2026 09:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | ipv6: avoid divide by zero in rt6_multipath_rebalance | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2026-09-16T08:48:26.343Z
Updated: 2026-10-19T08:52:44.129Z
Reserved: 2026-09-11T19:38:34.766Z
Link: CVE-2026-89790
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-16T09:17:09.827
Modified: 2026-10-19T09:18:22.690
Link: CVE-2026-89790
Redhat
No data.