Improper Initialization in Linux kernel - CVE-2026-63950

Vulnerability identifier: #VU138703

CSH Severity: Low

CVSS v4: 5.7 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63950

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.

The vulnerability exists due to improper initialization in try_to_unmap_one() in mm/rmap.c when reclaiming a lazyfree anonymous folio with device-exclusive page table entries. A local user can trigger reclaim after arranging the affected memory state to cause a denial of service.

Exploitation requires a sequence involving a MAP_ANONYMOUS | MAP_DROPPABLE mapping, MADV_FREE, and making the last page device-exclusive via HMM_DMIRROR_EXCLUSIVE.

Linux kernel
Ubuntu
linux-ibm (Ubuntu package)
linux-azure (Ubuntu package)
linux-aws (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-nvidia-bos (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux-ibm (Ubuntu package) - addressed in versions 7.0.0-1008.8, 7.0.0-1010.10
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1010.10
linux-aws (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1015.15
linux-nvidia (Ubuntu package) - addressed in versions 7.0.0-1016.16, 7.0.0-1016.16~24.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2016.16

• https://git.kernel.org/stable/c/0fcc34d0d8fefca4fea349e45c10e3a3d90350eb
• https://git.kernel.org/stable/c/3f8968e9cbf95d5d87d32218906cab0b9b9eddbe
• https://git.kernel.org/stable/c/f611db9b771b2b6775357555d2517af044fca4f0

• Improper Initialization in Linux kernel mm
• Ubuntu update for linux-ibm
• Ubuntu update for linux-azure
• Ubuntu update for linux-aws
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia