CVE-2026-45592: Windows Privilege Escalation in wininet.dll (Integer Overflow)

Technical summary

CVE-2026-45592 is an integer overflow or wraparound vulnerability (CWE-190) in the wininet.dll component of Windows, coupled with a use-after-free condition (CWE-416). The flaw allows an authenticated local attacker to trigger memory corruption through improper integer handling, leading to arbitrary code execution with SYSTEM privileges. The vulnerability requires Local execution context and Privilege level access, but operates without requiring User Interaction, making it a viable privilege escalation vector for attackers who have already gained initial access to a Windows system with standard user rights.

Business impact

Organizations running affected Windows versions face a significant privilege escalation risk. An attacker who compromises a standard user account—through phishing, malware, or software exploitation—can escalate to SYSTEM level without additional user action. This could lead to full system compromise, lateral movement within a network, data exfiltration, persistent backdoor installation, or ransomware deployment. The impact is heightened in environments where standard user accounts are prevalent and administrative controls are not granular.

Affected systems

The vulnerability affects Windows 10 (versions 1607, 1809, 21H2, and 22H2), Windows 11 (versions 23H2, 24H2, 25H2, and 26H1), and Windows Server editions 2012 through 2025. This is a broad attack surface spanning consumer, enterprise, and server deployments. Organizations relying on legacy Windows 10 versions like 1607 and 1809 should note these editions are in extended support phases and may have limited patch availability timelines.

Exploitability

The vulnerability is not currently listed on CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating no known public exploitation in the wild at publication. However, the straightforward attack prerequisites—local access plus a standard user account—make this a practical target for post-compromise privilege escalation. The lack of user interaction requirement increases the appeal to threat actors once initial access is established. Security researchers and malicious actors will likely develop working exploits following public disclosure.

Remediation

Organizations must apply security updates from Microsoft addressing CVE-2026-45592 across all affected Windows 10, Windows 11, and Windows Server versions. Verify patch applicability against Microsoft's official security advisory to confirm version-specific updates. Interim mitigations include enforcing least-privilege access principles, disabling or restricting wininet.dll usage where feasible, and monitoring for suspicious privilege escalation attempts in logs.

Patch guidance

Consult Microsoft's security bulletin for CVE-2026-45592 to identify patch versions specific to your Windows release. Windows 10 and 11 users should enable automatic updates or manually check Windows Update. Windows Server administrators should validate patch compatibility in test environments before production deployment, particularly for Server 2012 which is in extended support. Prioritize patching systems that host sensitive services or user-facing applications where standard user account compromise is likely.

Detection guidance

Monitor Windows event logs (Security and System channels) for failed privilege escalation attempts, unexpected SYSTEM-level process spawning from standard user sessions, and wininet.dll crash or fault indicators. Endpoint detection and response (EDR) tools should flag suspicious memory operations or integer arithmetic anomalies within wininet.dll execution. Hunt for unusual calls to SetFilePointer, WriteFile, or CreateProcess originating from processes linked to wininet functionality. Log and alert on unexpected elevation of privilege event IDs (4672 and 4688) correlated with Internet-related process execution.

Why prioritize this

This vulnerability merits immediate prioritization due to its HIGH CVSS score (7.8), broad affected product range, local privilege escalation impact, and lack of user interaction requirement. While not yet exploited in the wild, the attack chain—initial compromise followed by privilege escalation—is common in real-world incidents. Windows Server environments and systems running legacy Windows 10 versions should be prioritized, as they often host critical services and may have longer patch cycles.

Risk score, explained

The CVSS 3.1 score of 7.8 (HIGH) reflects the combination of local attack vector, low attack complexity, requirement for low privilege level, and complete impact on confidentiality, integrity, and availability. The score appropriately captures the risk to systems where user-level compromise is plausible and the attacker can immediately escalate to SYSTEM. The absence of network accessibility and user interaction requirement prevents a CRITICAL rating, but the breadth of affected systems and practical exploitability push this into the upper range of HIGH severity.

Frequently asked questions