Improper initialization in Linux kernel - CVE-2026-98546

Vulnerability identifier: #VU156848

CSH Severity: Low

CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-98546

CWE-ID: CWE-665

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to cause a denial of service by crashing the host.

The vulnerability exists due to improper initialization of the HDFGWTR2_EL2 trap-control register in the arm64 __init_el2_fgt2() function when configuring performance-monitoring register traps. A local user can write to PMZR_EL0 from EL0 to trigger an unhandled EL2 trap and a BUG() in the nVHE hypervisor, bringing down the host.

The described exploitation path requires kernel.perf_user_access=1 and a task with a user-read performance event, for which the PMU driver sets PMUSERENR_EL0.UEN.

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/071f51188a5d8ec10535541255587976d12fc7d8
• https://git.kernel.org/stable/c/2bc6b218717b9d08f466f88209251d54bc09b207
• https://git.kernel.org/stable/c/bb8c90c86441c090e9036f019cf1b4d7894a2c40
• https://git.kernel.org/stable/c/ce71865bf43f88bed9d9218e9218e537150be506

• Improper initialization in Linux kernel include asm
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more