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Microsoft April 2026 Patch Tuesday fixes 167 vulnerabilities and two zero

Notebookcheck • April 15, 2026

Microsoft released its April 2026 Patch Tuesday update on April 14, 2026, which addresses more than 160 security vulnerabilities, including two zero-day flaws, one of which was reported as actively exploited before patches became available.

The monthly rollout includes cumulative updates for supported Windows versions. Windows 11 versions 25H2 and 24H2 receive KB5083769 , while Windows 11 version 23H2 receives KB5082052 . These updates install automatically on most consumer devices unless Windows Update has been paused.

Security researchers described the April release as larger than average, with a higher-than-usual number of fixes affecting core Windows components.

Different security vendors reported slightly different vulnerability counts for April.

Microsoft addressed 167 vulnerabilities, including one actively exploited zero-day and one publicly disclosed vulnerability before release. Other security firms, including Qualys , reported totals closer to 163 to 164 vulnerabilities, with eight rated Critical.

Despite minor differences in counting methods, researchers broadly agree that April’s update cycle includes:

Zero-day vulnerabilities typically increase urgency because they may already be known to attackers before patches are released.

Microsoft’s primary Windows 11 update for April is KB5083769 , which updates systems to new builds after installation:

In addition to security fixes, the update includes reliability improvements and ongoing security hardening changes. Microsoft also introduced protections related to Remote Desktop usage, including warnings when opening unfamiliar .rdp configuration files.

These changes are part of Microsoft’s broader effort to reduce credential theft and phishing attacks that rely on remote connection tools.

Microsoft also published security updates for earlier Windows versions as part of the April cycle. Windows 11 version 23H2 received KB5082052, while supported Windows 10 systems received their own cumulative security updates.

Microsoft classifies these updates as mandatory because they address security vulnerabilities discovered in recent months. Systems configured for automatic updates will typically install them without user action.

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

BlueHammer Zero-Day Exploit Released, Exposing Windows Users to Privilege Escalation A security researcher, known as Chaotic Eclipse, has publicly released exploit code for a zero-day vulnerability in Windows, dubbed BlueHammer, allowing local privilege escalation to SYSTEM or elevated administrator privileges. The exploit targets a flaw in the Windows Defender update mechanism and has no available patch, leaving potentially over 1 billion Windows users vulnerable. The researcher expressed frustration with Microsoft's Security Response Center (MSRC) regarding their handling of the vulnerability disclosure process, leading to the public release of the exploit. Will Dormann, a principal vulnerability analyst, confirmed the exploit's functionality, noting that it is not entirely reliable and primarily affects local user accounts. The exploit code is available on GitHub, with significant interest from both security researchers and potential attackers. Microsoft has not yet issued a statement regarding a patch or a timeline for addressing the vulnerability. The exploit's release has raised concerns about the implications for cybersecurity, as attackers could leverage this flaw for malicious purposes. 130 sources 67

Extracted Entities

Microsoft April 2026 Patch Tuesday fixes 167 vulnerabilities and two zero

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Extracted Entities

Attack Types (2)

MITRE ATT&CK (2)

Platforms (2)