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Microsoft no longer claims that Windows 11 has all the protection that you need
Tech Optimizer
June 2, 2026

Microsoft no longer claims that Windows 11 has all the protection that you need

In April, Microsoft published a blog post discussing the security features of Windows 11, emphasizing that its built-in protections, such as Microsoft Defender Antivirus and SmartScreen, may eliminate the need for third-party antivirus solutions for many users. The blog highlighted that adequate security could be maintained with default settings, regular updates, and intentional software downloads. However, it also noted that users with specific needs, like managing multiple devices or requiring additional features, might still consider third-party software. The blog post was removed from the Microsoft Learning Center without formal announcement, raising questions about the company's communication strategy.
CVE-2026-45585: YellowKey BitLocker Bypass
Winsage
May 23, 2026

CVE-2026-45585: YellowKey BitLocker Bypass

BitLocker, a security feature for data protection, has a vulnerability identified as CVE-2026-45585, also known as YellowKey, which allows unauthorized access to encrypted data on Windows 11 versions 24H2, 25H2, 26H1, and Windows Server 2025. This flaw does not compromise BitLocker’s encryption but affects the recovery environment supporting it. The vulnerability can be exploited locally through the Windows Recovery Environment (WinRE) by an attacker with physical access, who can trigger an unrestricted shell and access the BitLocker-protected volume. Microsoft has provided two mitigation strategies: modifying the WinRE image to remove the autofstx.exe entry and transitioning from TPM-only protection to a TPM+PIN requirement at startup. The exploit poses challenges for detection, as it occurs pre-boot and currently lacks vendor-published indicators of compromise. Organizations using BitLocker for unattended devices are particularly at risk, as the vulnerability can lead to loss of confidentiality if an attacker gains access before the legitimate user.
Microsoft says public sharing of Windows 11 vulnerability violates 'best practices'
Winsage
May 22, 2026

Microsoft says public sharing of Windows 11 vulnerability violates ‘best practices’

A security researcher known as Nightmare-Eclipse revealed a vulnerability in Windows 11, named YellowKey, which allows attackers to access BitLocker-encrypted drives through the Windows Recovery Environment. Microsoft acknowledged the vulnerability, assigned it the identifier CVE-2026-45585, and criticized the public sharing of its proof of concept. Currently, there is no patch available for the BitLocker bypass, but physical access to the device provides some protection. The vulnerability does not exist in Windows 10 due to differences in the Windows Recovery Environment. The attack requires a stolen Windows 11 laptop and a USB stick, and the vulnerable filesystems include NTFS, FAT32, and exFAT. Nightmare-Eclipse speculated that the bypass may function as a backdoor, while Microsoft referred to it as a "security feature bypass vulnerability."
Microsoft Defender Zero-Day Vulnerabilities RedSun and UnDefend Actively Exploited on Windows 10, 11, and Server (April 2026 CVE Analysis)
Winsage
May 21, 2026

Microsoft Defender Zero-Day Vulnerabilities RedSun and UnDefend Actively Exploited on Windows 10, 11, and Server (April 2026 CVE Analysis)

In April 2026, two zero-day vulnerabilities, RedSun and UnDefend, were discovered in Microsoft Defender, affecting Windows 10, Windows 11, and Windows Server platforms. These vulnerabilities allow attackers to escalate privileges to SYSTEM and bypass Defender’s protections. RedSun exploits a flaw in Defender's remediation process, enabling low-privileged users to overwrite critical system files. UnDefend allows attackers to disrupt Defender’s updates, keeping it outdated and ineffective. Both vulnerabilities are actively being exploited, with attackers leveraging them to gain persistent access and deploy ransomware. The primary targets are organizations using Windows systems with Defender enabled, particularly in sectors like finance, healthcare, and government. Mitigation strategies include applying updates for related vulnerabilities, monitoring for suspicious activities, and implementing additional security measures.
Microsoft shares mitigation for YellowKey Windows zero-day
Winsage
May 20, 2026

Microsoft shares mitigation for YellowKey Windows zero-day

Microsoft has addressed the YellowKey vulnerability, a zero-day flaw in Windows BitLocker identified as CVE-2026-45585. This vulnerability allows unauthorized access to BitLocker-protected drives through a specific exploitation process involving 'FsTx' files. The flaw was disclosed by an anonymous researcher known as 'Nightmare Eclipse.' Microsoft has released mitigation strategies, including removing the autofstx.exe entry from the Session Manager's BootExecute REGMULTISZ value and reestablishing BitLocker trust for WinRE. Additionally, users are advised to change BitLocker settings from "TPM-only" to "TPM+PIN" mode, requiring a pre-boot PIN for drive decryption, and to enable "Require additional authentication at startup" for unencrypted devices.
Microsoft confirms Windows 11 security update install issues
Winsage
May 18, 2026

Microsoft confirms Windows 11 security update install issues

Microsoft has acknowledged a significant issue with the May 2026 Windows 11 security update, KB5089549, where users are encountering difficulties in installation, specifically the 0x800f0922 error code. This issue is primarily due to insufficient free space on the EFI System Partition (ESP), especially for devices with 10 MB or less available. The installation may fail during the reboot phase at around 35–36% completion, with users receiving notifications like "Something didn't go as planned. Undoing changes." Log entries may indicate insufficient ESP free space, such as "SpaceCheck: Insufficient free space" and "ServicingBootFiles failed. Error = 0x70." Microsoft recommends affected users utilize the Known Issue Rollback feature to reverse problematic updates and advises IT departments to install and configure the relevant Group Policy to address the issue.
Microsoft Patch Tuesday for May 2026 — Snort rules and prominent vulnerabilities
Winsage
May 13, 2026

Microsoft Patch Tuesday for May 2026 — Snort rules and prominent vulnerabilities

Microsoft's May 2026 security update addresses 137 vulnerabilities, with 31 classified as critical. None of these critical vulnerabilities are currently being exploited in active attacks. Sixteen of the critical vulnerabilities involve remote code execution (RCE) issues in Microsoft products, including Microsoft Office, Microsoft Word, and Azure. Specific vulnerabilities include: - CVE-2026-32161: A use-after-free vulnerability in the Windows Native WiFi Miniport Driver. - CVE-2026-40358: A use-after-free vulnerability in Microsoft Office. - CVE-2026-41089: A stack-based buffer overflow in Windows Netlogon. Additional important vulnerabilities flagged include: - CVE-2026-33835: Windows Cloud Files Mini Filter Driver Elevation of Privilege Vulnerability. - CVE-2026-33837: Windows TCP/IP Local Elevation of Privilege Vulnerability. - CVE-2026-35416: Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability. Talos is releasing a new Snort ruleset to detect attempts to exploit these vulnerabilities, and users are advised to update their Cisco Security Firewalls and acquire the latest rule pack via Snort.org.
RedSun: Windows 0day when Defender becomes the attacker
Winsage
April 18, 2026

RedSun: Windows 0day when Defender becomes the attacker

A vulnerability has been discovered in Windows Defender that allows standard users to exploit a logic error in the file remediation process, enabling code execution with elevated privileges without administrative access. This flaw, identified by security researcher Chaotic Eclipse, occurs because Windows Defender does not verify if the restoration location of flagged files has been altered through a junction point. The exploit, named RedSun, takes advantage of a missing validation in the MpSvc.dll file, allowing attackers to redirect file restoration to the C:WindowsSystem32 directory. RedSun operates by chaining together four legitimate Windows features: Opportunistic Locks (OPLOCKs), Cloud Files API, Volume Shadow Copy Service (VSS), and Junction Points. The execution of the exploit involves monitoring shadow copies, triggering Defender's detection, synchronizing OPLOCKs, and ultimately writing malicious binaries to the System32 directory. The root cause is the lack of reparse point validation in the restoration process, and currently, no patch or CVE has been assigned for this vulnerability. It affects Windows 10, Windows 11, and Windows Server 2019 and later, and organizations are advised to implement behavioral detection strategies until a fix is available.
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