Use of Uninitialized Variable in Linux kernel - CVE-2026-63837

Vulnerability identifier: #VU138812

CSH Severity: Low

CVSS v4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63837

CWE-ID: CWE-457

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to disclose sensitive information.

The vulnerability exists due to use of uninitialized memory in ena_phc_gettimex64() when handling a PTP ioctl after ena_com_phc_get_timestamp() returns an error. A local user can invoke the affected ioctl to disclose sensitive information.

The issue can occur when PHC is disabled or in a blocked state, and invalid hardware values may also be exposed to userspace.

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/24a08d7d6218d60c033015cf4870b6096446e734
• https://git.kernel.org/stable/c/bddf59818ae5102e6d82a4dae5add6df8da38fb0
• https://git.kernel.org/stable/c/edcb049d836e175e7b3d5e0d05657104545b5e65

• Use of Uninitialized Variable in Linux kernel amazon ena driver
• 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