NULL pointer dereference in Linux kernel - CVE-2026-63877

Vulnerability identifier: #VU138777

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-2026-63877

CWE-ID: CWE-476

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local attacker to cause a denial of service.

The vulnerability exists due to a null pointer dereference in the dz serial driver when initializing the first serial port. A local attacker can trigger serial port initialization to cause a denial of service.

The crash occurs because a pointer derived from a null parent-device pointer is dereferenced during early system bootstrap.

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/2ff0401ffddaccc85f758c8259912d686d052b31
• https://git.kernel.org/stable/c/5c9fb95c8d6430d11dbb7b44fbe23222585cda86
• https://git.kernel.org/stable/c/5d7a49d60b8fda66da60e240fd7315232fa1754f
• https://git.kernel.org/stable/c/6f59646229490a93cda950017ad4bdfbfe770a1d
• https://git.kernel.org/stable/c/c9e78361fe92fb64662fc3c8f34e2cdbb8c25bc6

• 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