NULL pointer dereference in Linux kernel - CVE-2026-63876

Vulnerability identifier: #VU138776

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-2026-63876

CWE-ID: CWE-476

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 a null pointer dereference in the zs serial driver during serial port initialization when initializing the first serial port. A local user can trigger driver initialization to cause a denial of service.

The issue can crash the kernel during system bootstrap on affected DECstation systems.

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/237dc8c08de3cb293b6607aaee8b13b3a671e267
• https://git.kernel.org/stable/c/4dc9f1517503c883d5ce25b7ab29d177d05edc6a
• https://git.kernel.org/stable/c/6a83d5e24a84e746425cd93539130e5f7381ef47
• https://git.kernel.org/stable/c/7cac59d08a73cb866ec51a483a6f3fe0f531947c
• https://git.kernel.org/stable/c/bb2040484f90f91b717060e1a66026cc4287bcf0

• NULL pointer dereference in Linux kernel tty serial 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