Improper update of reference count in Linux kernel - CVE-2026-72218

Vulnerability identifier: #VU143377

CSH Severity: Medium

CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-72218

CWE-ID: CWE-911

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote user to cause a denial of service.

The vulnerability exists due to improper reference count management in lockd nlm_lookup_file() when handling cached file lookups after nlm_do_fopen() failure. A remote user can trigger a failed file-open operation to cause a denial of service.

The issue occurs because the file reference count is incremented but not released, preventing the file from being reaped between requests.

Linux kernel
Ubuntu
linux-nvidia (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux-azure-7.0 (Ubuntu package)
linux-azure (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux-nvidia (Ubuntu package) - addressed in versions 5.15.0-1112.113, 5.15.0.1112.112
linux-gcp-7.0 (Ubuntu package) - addressed in versions 7.0.0-38.38~24.04.4, 7.0.0-1013.13~24.04.1, 7.0.0-1014.14~24.04.1
linux (Ubuntu package) - addressed in versions 7.0.0-38.38, 7.0.0-38.38.1, 7.0.0-1008.9, 7.0.0-1013.13~24.04.1, 7.0.0-1014.14, 7.0.0-1015.15
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1015.15
linux-azure-7.0 (Ubuntu package) - addressed in versions 7.0.0-1016.16~24.04.1, 7.0.0-1017.17~24.04.1
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1016.16, 7.0.0-1017.17

• https://git.kernel.org/stable/c/3a5c55a19cad62f2973be25fe96a1a9e7f618e8a
• https://git.kernel.org/stable/c/46d59ff421824b6483549d87f14efffbbbd1f6cb
• https://git.kernel.org/stable/c/6cd84cefd8b73e85b9eda17b319bd40a670f3a38
• https://git.kernel.org/stable/c/70a38f87bed7f0694fd07988b47b2db1e10d8df3
• https://git.kernel.org/stable/c/7ce4c23e783e766507b2cef27bbf97e9ca944f1a
• https://git.kernel.org/stable/c/84008bf1860e0ef8059a7583a1163f36b704d08a
• https://git.kernel.org/stable/c/cb3420c047957e565101585bb4f15e1a6e3de6b0
• https://git.kernel.org/stable/c/fe3b45b56b6c3d4b6b341de27fa291005287a21c

• Improper update of reference count in Linux kernel lockd
• Ubuntu update for linux-gcp-7.0
• Ubuntu update for linux-nvidia
• Ubuntu update for linux-azure-7.0
• Ubuntu update for linux
• Ubuntu update for linux-azure
• Ubuntu update for linux-oem-7.0