CVE-2026-99121
Received
Received - Intake
Linux Kernel IPv4 Fib Rebalance Divide by Zero
Vulnerability report for CVE-2026-99121, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-28
Last updated on: 2026-10-28
Assigner: kernel.org
Description
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
