CVE-2026-62840 in Linux
Summary
by MITRE • 10/15/2026
Time-of-check time-of-use (toctou) race condition in Linux Kernel allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a classic Time-Of-Check-Time-Of-Use, or TOCTOU, race condition within the Linux kernel architecture. This class of flaw arises when a system performs a security check on a resource and subsequently uses that same resource without ensuring its state has remained unchanged between the two operations. In this specific instance, an authorized attacker can exploit the temporal gap to manipulate the underlying data structure or file permissions, thereby bypassing the initial validation logic. The core technical mechanism involves the kernel failing to maintain atomicity during critical privilege escalation sequences, allowing a local user to alter conditions such that the subsequent action proceeds under elevated privileges rather than the originally intended restricted context.
From an operational perspective, this vulnerability enables unauthorized local privilege escalation, effectively granting the attacker root-level access or equivalent administrative rights on the affected system. This transformation from a standard user account to a privileged entity allows for comprehensive control over the operating environment, including the ability to read sensitive data, modify system configurations, install malicious software, and persist across reboots if not properly addressed. The impact is severe because it undermines the fundamental security boundary between unprivileged users and the kernel, potentially leading to complete compromise of host integrity and confidentiality.
The technical flaw aligns with Common Weakness Enumeration identifier CWE-367, which defines TOCTOU race conditions as a failure to ensure that data has not changed since its last verification. In the context of Linux kernel development, such issues often stem from improper locking mechanisms or reliance on non-atomic operations when accessing shared resources like file descriptors, inode structures, or memory mappings. Attackers typically leverage high-frequency system calls and precise timing manipulation to trigger the race window before the kernel completes its security checks. This requires local access but no special hardware privileges beyond standard user execution rights, making it a significant threat vector for multi-tenant environments and shared hosting platforms where lateral movement is facilitated by such escalations.
Mitigation strategies primarily involve applying vendor-provided patches that address the specific race condition within the kernel source code. These updates typically introduce proper synchronization primitives, such as mutexes or spinlocks, to ensure atomicity during critical checks and uses. Additionally, implementing mandatory access control systems like SELinux or AppArmor can provide an additional layer of defense by restricting what actions even a privileged process can perform, thereby limiting the blast radius if exploitation occurs. System administrators should prioritize immediate patching for affected kernel versions and monitor system logs for unusual patterns indicative of race condition attempts, such as rapid successive calls to specific syscalls associated with file or permission management.