CVE-2026-45592 Overview
CVE-2026-45592 is an integer overflow vulnerability in the Windows Internet (wininet.dll) component. The flaw allows an authorized local attacker to elevate privileges on affected Microsoft Windows systems. The weakness is classified under [CWE-190] Integer Overflow or Wraparound.
Microsoft published the advisory on June 9, 2026. The vulnerability affects a broad range of Windows 10, Windows 11, and Windows Server releases. Exploitation requires local access and low privileges but no user interaction. Successful exploitation results in high impact to confidentiality, integrity, and availability.
Critical Impact
An authenticated local attacker can trigger an integer wraparound in wininet.dll to elevate privileges, gaining full control over the affected Windows host.
Affected Products
- Microsoft Windows 10 (versions 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (versions 23H2, 24H2, 25H2, 26H1)
- Microsoft Windows Server 2012 R2, 2016, 2019, 2022, and 2025
Discovery Timeline
- 2026-06-09 - CVE-2026-45592 published to NVD
- 2026-06-11 - Last updated in NVD database
Technical Details for CVE-2026-45592
Vulnerability Analysis
The vulnerability resides in wininet.dll, the Windows component that provides HTTP, HTTPS, and FTP client functionality to applications. An integer overflow occurs when arithmetic operations on size or length values exceed the maximum representable value of the underlying integer type. The resulting wraparound produces a smaller-than-expected value that downstream code uses for buffer sizing or boundary checks.
When the miscalculated value reaches memory allocation or copy routines, the process writes data beyond the intended buffer. A local attacker with low privileges can craft inputs that trigger this overflow and corrupt adjacent memory structures. Controlled corruption inside a privileged process context yields elevation of privilege.
The EPSS score is 0.082%, reflecting low current exploit prediction. However, integer overflows in network stack components historically attract weaponization once technical details surface.
Root Cause
The root cause is missing or insufficient validation of arithmetic operations on user-influenced length or count values inside wininet.dll. Without bounds checking before allocation or copy operations, the wraparound condition propagates into memory-handling logic, classified as [CWE-190].
Attack Vector
The attack vector is local. An attacker must already execute code on the target system with at least low-privileged user rights. The attacker invokes the vulnerable code path in wininet.dll through a process that loads or interacts with the library. Crafted parameters trigger the overflow, and the resulting memory corruption is leveraged to execute attacker-controlled logic in a higher-privilege context.
No verified public exploit code is available at this time. Technical details of the affected function are not disclosed in the vendor advisory.
Detection Methods for CVE-2026-45592
Indicators of Compromise
- Unexpected crashes or Application Error events referencing wininet.dll in the Windows Event Log.
- Child processes spawned by applications that load wininet.dll running under SYSTEM or elevated tokens without prior administrative action.
- Anomalous loading of wininet.dll by unsigned or low-reputation binaries on the host.
Detection Strategies
- Hunt for process integrity level transitions where a Medium or Low integrity process spawns a High or System integrity child.
- Correlate Windows Error Reporting (WER) entries that reference faulting module wininet.dll with subsequent privileged process activity.
- Inspect endpoint telemetry for token manipulation or handle duplication events following wininet.dll faults.
Monitoring Recommendations
- Enable Microsoft Defender exploit protection telemetry and forward Sysmon Event IDs 1, 7, 10, and 11 to a central log store.
- Monitor for newly installed binaries that statically link to or dynamically load wininet.dll from non-standard paths.
- Track privilege escalation patterns aligned to MITRE ATT&CK T1068 across all Windows endpoints and servers.
How to Mitigate CVE-2026-45592
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update CVE-2026-45592 advisory to all affected Windows clients and servers.
- Prioritize patching multi-user systems, jump hosts, and terminal servers where local accounts have shell access.
- Audit local user accounts and remove unnecessary interactive logon rights to reduce the population of potential attackers.
Patch Information
Microsoft has released security updates for all affected Windows 10, Windows 11, and Windows Server versions listed in the advisory. Refer to the Microsoft Security Update CVE-2026-45592 for the cumulative update KB number that matches each build. Deploy via Windows Update, WSUS, Microsoft Endpoint Configuration Manager, or Intune.
Workarounds
- No vendor-supplied workaround removes the vulnerability without the patch; restrict local logon rights as a compensating control.
- Enforce application allowlisting through Windows Defender Application Control or AppLocker to limit which binaries can invoke wininet.dll.
- Enable Attack Surface Reduction rules that block credential theft and child process creation from Office and scripting hosts.
# Verify installed patch level on a Windows host
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10
# Confirm wininet.dll file version after patch deployment
(Get-Item C:\Windows\System32\wininet.dll).VersionInfo
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
