CVE-2026-99121

ipv4: avoid divide by zero in fib_rebalance

State: Published
Severity: Not scored
Published: Oct 28, 2026
Updated: Oct 30, 2026
Reserved: Sep 25, 2026

Description

In the Linux kernel, the following vulnerability has been resolved:

ipv4: avoid divide by zero in fib_rebalance

fib_rebalance() computes the total eligible nexthop weight in one pass and programs upper bounds in a second pass. A concurrent change to ignore_routes_with_linkdown can make the first pass return zero while the second pass sees an eligible nexthop, resulting in division by zero.

If the first pass reports a zero total, set each nexthop upper bound to -1 and skip the division. This matches the IPv6 fix in commit d2c26c2911dd ("ipv6: avoid divide by zero in rt6_multipath_rebalance") and preserves the lock-free rebalance path.

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	0e884c78ee19e902f300ed147083c28a0c6302f0 to before baf3a767b2845eb8e68f056ee4aa5b41b151e990Affected 0e884c78ee19e902f300ed147083c28a0c6302f0 to before f655a26490e705ec76a79db7f412847fda342b39Affected 0e884c78ee19e902f300ed147083c28a0c6302f0 to before 7c68f4de5090b17b63b9a0a3b01b3807e01a296aAffected 0e884c78ee19e902f300ed147083c28a0c6302f0 to before 226a974054acbd892560bfa67f0ae8ffe271a736Affected 0e884c78ee19e902f300ed147083c28a0c6302f0 to before 0800c92ca5d1983df6843a5435299978901d1d02Affected 0e884c78ee19e902f300ed147083c28a0c6302f0 to before 5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8fAffected 0e884c78ee19e902f300ed147083c28a0c6302f0 to before d5520e815c4b1427104ce1428ee23821f2aa824dAffected 0e884c78ee19e902f300ed147083c28a0c6302f0 to before 5046d2880fec7d49ebed2fd2866747ee1d06ad71Affected
LinuxLinux	4.4Affected before 4.4Not affected 5.10.273 through 5.10.Not affected 5.15.224 through 5.15.Not affected 6.1.191 through 6.1.Not affected 6.6.161 through 6.6.Not affected 6.12.115 through 6.12.Not affected 6.18.59 through 6.18.Not affected 7.2.13 through 7.2.*Not affected 7.3 and laterNot affected

Product

Versions

LinuxLinux

0e884c78ee19e902f300ed147083c28a0c6302f0 to before baf3a767b2845eb8e68f056ee4aa5b41b151e990Affected
0e884c78ee19e902f300ed147083c28a0c6302f0 to before f655a26490e705ec76a79db7f412847fda342b39Affected
0e884c78ee19e902f300ed147083c28a0c6302f0 to before 7c68f4de5090b17b63b9a0a3b01b3807e01a296aAffected
0e884c78ee19e902f300ed147083c28a0c6302f0 to before 226a974054acbd892560bfa67f0ae8ffe271a736Affected
0e884c78ee19e902f300ed147083c28a0c6302f0 to before 0800c92ca5d1983df6843a5435299978901d1d02Affected
0e884c78ee19e902f300ed147083c28a0c6302f0 to before 5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8fAffected
0e884c78ee19e902f300ed147083c28a0c6302f0 to before d5520e815c4b1427104ce1428ee23821f2aa824dAffected
0e884c78ee19e902f300ed147083c28a0c6302f0 to before 5046d2880fec7d49ebed2fd2866747ee1d06ad71Affected

LinuxLinux

4.4Affected
before 4.4Not affected
5.10.273 through 5.10.*Not affected
5.15.224 through 5.15.*Not affected
6.1.191 through 6.1.*Not affected
6.6.161 through 6.6.*Not affected
6.12.115 through 6.12.*Not affected
6.18.59 through 6.18.*Not affected
7.2.13 through 7.2.*Not affected
7.3 and laterNot affected

References

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