Reliance on undefined behavior in Linux kernel - CVE-2026-98585

Vulnerability identifier: #VU156888

CSH Severity: Low

CVSS v4: 4.6 [CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-98585

CWE-ID: CWE-758

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local privileged user to trigger undefined kernel behavior that may disrupt system operation.

The vulnerability exists due to an undefined arithmetic operation on zero in the fbnic Ethernet driver's fbnic_set_ringparam() function when processing ring-size settings supplied through ethtool. A local privileged user can submit a zero ring size that reaches roundup_pow_of_two() before minimum-size validation to trigger undefined behavior that may disrupt system operation.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17

• https://git.kernel.org/stable/c/0160953d8eec75c3c55562158c46442ff1fd410b
• https://git.kernel.org/stable/c/491aa3167ae02f219cb2d2de6f4196d28dca03be
• https://git.kernel.org/stable/c/92c9f2ea634d92adff5403d231ebeda683c5685a

• Reliance on undefined behavior in Linux kernel meta fbnic driver
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more