CVE-2026-49800 in Windows
Summary
by MITRE • 07/14/2026
Integer overflow or wraparound in Windows Web Proxy Auto-Discovery Protocol (WPAD) allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 07/15/2026
The vulnerability described represents a critical integer overflow condition within the Windows Web Proxy Auto-Discovery Protocol implementation that can be exploited by authenticated attackers to achieve local privilege escalation. This flaw exists in how the system handles integer arithmetic during proxy configuration processing, specifically when parsing or validating proxy auto-discovery scripts. The vulnerability stems from insufficient input validation and boundary checking mechanisms that fail to properly handle cases where integer values exceed their maximum representable range, leading to wraparound behavior that can be manipulated for malicious purposes.
From a technical perspective, the integer overflow occurs during the processing of proxy configuration data structures where unsigned integers are incremented or decremented beyond their maximum value, causing them to wrap around to zero or negative values. This wraparound creates predictable memory access patterns and buffer manipulation opportunities that attackers can leverage to overwrite critical system structures or execute arbitrary code with elevated privileges. The vulnerability is particularly dangerous because it requires only local authentication, making it accessible to any user who has logged into the system, regardless of their initial privilege level.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables attackers to gain SYSTEM-level access on affected Windows systems, potentially leading to complete system compromise and lateral movement within network environments. Attackers can exploit this condition to install persistent backdoors, exfiltrate sensitive data, or deploy additional malicious payloads without requiring additional attack vectors such as remote code execution or credential theft. The vulnerability affects multiple Windows versions including windows 10, windows server 2016, and later releases where the web proxy auto-discovery protocol functionality remains active.
Security practitioners should implement immediate mitigations including applying Microsoft security updates that address the integer overflow condition in the wpad implementation, disabling unnecessary proxy auto-discovery features when not required for network operations, and monitoring system logs for unusual proxy configuration changes or authentication patterns. The vulnerability maps to CWE-190 Integer Overflow or Wraparound which is categorized under weak input validation and improper arithmetic handling within software security frameworks. From an attack perspective, this represents a privilege escalation technique that aligns with ATT&CK tactic TA0004 Privilege Escalation and technique T1068 Local Privilege Escalation, making it a significant concern for enterprise security teams managing windows-based environments.
Organizations should conduct comprehensive vulnerability assessments to identify systems running affected wpad implementations and establish monitoring procedures to detect potential exploitation attempts. The remediation approach must include not only applying patches but also implementing network segmentation controls that limit local access to systems with proxy configuration capabilities, as well as establishing robust endpoint detection and response capabilities that can identify anomalous behavior patterns associated with integer overflow exploitation attempts. Regular security awareness training should emphasize the importance of keeping systems updated and monitoring for unusual local privilege escalation activities that may indicate exploitation of such vulnerabilities in the web proxy infrastructure components.