CVE-2026-70122 in Windows
Summary
by MITRE • 10/14/2026
Time-of-check time-of-use (toctou) race condition in Windows Broadcast DVR User Service allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a classic Time-of-Check-Time-of-Use, or TOCTOU, race condition within the Windows Broadcast DVR User Service. This specific class of flaw arises from a fundamental timing discrepancy in how the operating system handles security checks versus resource access operations. In this scenario, the service performs an authorization check to verify if a user has permission to perform a certain action, but between that verification and the actual execution of the privileged operation, there is a window of opportunity where the underlying state can be altered by another process or thread. An authorized attacker who already possesses local access on the system can exploit this race condition to manipulate the environment such that the service acts upon stale or manipulated data, effectively bypassing the intended security controls and executing actions with higher privileges than originally granted.
From a technical perspective, TOCTOU vulnerabilities are particularly insidious because they do not rely on incorrect logic in isolation but rather on the non-atomic nature of certain system calls when subjected to concurrent access. The Windows Broadcast DVR User Service likely retrieves file paths, registry keys, or other resources during the check phase and then re-accesses them during the use phase without ensuring that these resources remain unchanged. If an attacker can rapidly create, delete, or modify a symbolic link, temporary file, or environment variable within this narrow time window, they can redirect the service to interact with a controlled resource instead of the intended one. This redirection allows the attacker to write data into protected system directories, overwrite critical configuration files, or execute arbitrary code under the context of the elevated service account, thereby achieving local privilege escalation from a standard user level to that of SYSTEM or other high-privilege identities.
The operational impact of this vulnerability is severe due to its potential for complete system compromise. Once an attacker successfully exploits this race condition and elevates their privileges, they gain unrestricted access to all data on the machine, including sensitive corporate information, personal credentials, and cryptographic keys stored in memory or on disk. This level of access allows the attacker to install persistent backdoors, disable security monitoring tools such as antivirus software or Windows Defender, and move laterally across a network if the compromised host is connected to one. The existence of this flaw undermines the principle of least privilege, which assumes that users running with standard rights cannot affect system integrity unless explicitly authorized through secure mechanisms.
To mitigate this vulnerability, organizations should prioritize applying the latest security patches released by Microsoft for Windows systems containing the Broadcast DVR User Service. These updates typically involve refactoring the affected code to ensure atomic operations or using more robust access control methods such as kernel-mode object handles that do not suffer from path-based race conditions. In environments where patching is delayed, administrators can mitigate risk by disabling the vulnerable service if it is not required for business operations. This involves stopping the Broadcast DVR User Service and setting its startup type to disabled via services.msc or PowerShell cmdlets like Set-Service. Additionally, enforcing strict file system permissions on directories that might be targeted in such race conditions can reduce the attack surface, although this is a less effective defense than patching since TOCTOU flaws often exploit internal service logic rather than external permission misconfigurations alone.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-367, which defines Time-of-check Time-of-use (TOCTOU) Race Conditions as the use of information that can be changed between the time it is checked and the time it is used. Furthermore, in terms of tactical classification within the MITRE ATT&CK framework, this exploitation technique falls under Privilege Escalation techniques such as T1068 Exploitation for Privilege Escalation or potentially T1543 Create or Modify System Process if the race condition allows for service manipulation. Understanding these mappings helps security teams categorize the threat correctly and apply appropriate detection rules focused on monitoring unusual activity patterns in system services, particularly those involving rapid file creation or modification events associated with privileged processes.