CVE-2026-72947 in Windows
Summary
by MITRE • 09/09/2026
Integer underflow (wrap or wraparound) in Windows File History Service allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an integer underflow within the Windows File History Service represents a critical security flaw that compromises the integrity of privilege boundaries on affected systems. This specific type of memory corruption error occurs when arithmetic operations result in a value lower than the minimum representable value for the data type, causing the number to wrap around to a large positive value or an incorrect negative index depending on implementation details. In the context of system services like File History, which manages backups and file versioning tasks with elevated privileges, such miscalculations can lead to severe memory safety violations. The core technical flaw lies in how input parameters are validated before being used for buffer allocation or array indexing operations. When an attacker provides crafted inputs that trigger this underflow condition, the service may allocate insufficient memory space or access invalid memory addresses based on the wrapped-around value rather than the intended magnitude of the request.
From a technical perspective, integer underflows in Windows services often stem from improper handling of signed versus unsigned integers during size calculations. If a subtraction operation results in a negative number that is then cast to an unsigned type without proper checks, it becomes a very large positive integer. Subsequent operations relying on this value may proceed with the assumption that sufficient resources are available or that memory boundaries are respected. This discrepancy allows for buffer over-reads or potentially exploitable heap corruption scenarios if the service attempts to write data based on these miscalculated sizes. The presence of such flaws in a system component underscores the complexity of maintaining robust input validation across large codebases where legacy logic may not account for edge cases involving extreme numeric values.
The operational impact of this vulnerability is significant due to its potential for local privilege escalation. An authorized attacker, meaning someone who already has valid credentials and access to the machine, can exploit this flaw to execute arbitrary code with higher privileges than those originally granted. By leveraging the memory corruption caused by the integer underflow, an attacker could potentially overwrite critical control data structures such as function pointers or exception handlers within the service process space. This manipulation allows for the redirection of execution flow to malicious payloads injected into the vulnerable process context. Consequently, this leads to a complete compromise of system confidentiality, integrity, and availability, effectively granting the attacker administrative rights over the operating environment without detection by standard access control mechanisms.
This vulnerability aligns with Common Weakness Enumeration category CWE-192, which defines integer coercion errors that lead to buffer overflows or other memory safety issues. Furthermore, in terms of tactical classification under MITRE ATT&CK, this exploit path relates to techniques involving privilege escalation through exploitation of local vulnerabilities. Attackers typically utilize such flaws after gaining initial foothold access via phishing, malware delivery, or network exploits. The ability to escalate privileges locally is a critical step in lateral movement and persistence strategies within enterprise environments. Defenders must recognize that even authorized users pose risks if application logic contains fundamental programming errors like integer underflows, highlighting the need for rigorous code review practices focused on numeric type safety.
Mitigation strategies primarily involve applying vendor-supplied patches that correct the underlying arithmetic validation logic to prevent wraparound conditions from occurring during input processing. Security administrators should ensure that all systems running the affected Windows File History Service are updated with the latest security updates released by Microsoft. Additionally, implementing strict application whitelisting policies can restrict unauthorized execution of scripts or binaries within sensitive service contexts, thereby reducing the attack surface even if a vulnerability is present. Monitoring for anomalous behavior in system services, such as unexpected memory usage spikes or access to restricted registry keys, may also aid in detecting exploitation attempts before full compromise occurs. Regular audits of user permissions and adherence to least privilege principles further diminish the potential impact should an attacker succeed in exploiting this flaw.