Division by zero in Linux kernel - CVE-2026-99121
Published: October 29, 2026
Vulnerability identifier: #VU158475
CSH Severity: Low
CVSS v4: 5.6 [CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-99121
CWE-ID: CWE-369
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local privileged user to cause a denial of service through a potential kernel crash.
The vulnerability exists due to division by zero in the Linux kernel's fib_rebalance() function when a concurrent change to ignore_routes_with_linkdown causes inconsistent nexthop eligibility between its two passes. A local privileged user can trigger rebalancing during such a change to cause a division-by-zero fault that may crash the kernel.
Affected software
Linux kernel
Debian Linux
linux (Debian package)
Debian Linux
linux (Debian package)
How to mitigate CVE-2026-99121
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3
linux (Debian package) - update to 6.12.115-2
linux (Debian package) - update to 6.12.115-2