Improper locking in Linux kernel - CVE-2025-21900

Vulnerability identifier: #VU106803

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-2025-21900

CWE-ID: CWE-667

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to perform a denial of service (DoS) attack.

The vulnerability exists due to improper locking within the nfs4_atomic_open() function in fs/nfs/nfs4proc.c, within the nfs4_inode_return_delegation() function in fs/nfs/delegation.c. A local user can perform a denial of service (DoS) attack.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-lowlatency (Ubuntu package)

Install update from vendor's website.

Linux kernel - update to 6.13.6
linux (Ubuntu package) - addressed in versions 6.11.0-26.26, 6.11.0-26.26~24.04.1, 6.11.0-1010.10, 6.11.0-1013.13, 6.11.0-1015.15, 6.11.0-1015.15~24.04.1, 6.11.0-1022.22
linux-aws (Ubuntu package) - update to 6.11.0-1014.15
linux-lowlatency (Ubuntu package) - addressed in versions 6.11.0-1014.15, 6.11.0-1014.15~24.04.1, 6.11.0-1016.17

• https://git.kernel.org/stable/c/4fe4ae6c2e01d028856b73b6328b12b8945df871
• https://git.kernel.org/stable/c/8f8df955f078e1a023ee55161935000a67651f38
• https://git.kernel.org/stable/c/f41a60bc43e7abbc636fee78bed0d74c31e738b0
• https://mirrors.edge.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.13.6

• Improper locking in Linux kernel nfs
• Ubuntu update for linux
• Ubuntu update for linux-aws
• Ubuntu update for linux-lowlatency