Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel - CVE-2026-89917

Vulnerability identifier: #VU150374

CSH Severity: Low

CVSS v4: 5.7 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-89917

CWE-ID: CWE-367

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 time-of-check to time-of-use race condition in the Arm64 KVM nested virtualization VNCR mapping logic when concurrent VNCR TLB invalidation and vcpu_put() unmapping occur. A local user can trigger the concurrent operations to cause a denial of service.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17

• https://git.kernel.org/stable/c/38640bc32be3fcf9526d477155bc19d3f146231f
• https://git.kernel.org/stable/c/5cbd8761d001c11ada73b1753d772c4745a70e72
• https://git.kernel.org/stable/c/9065c1261f8a05c6a7a2d90048c7c0665ab2896d

• Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel arm64 kvm
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more