Microsoft fixed 120 vulnerabilities on Tuesday - 17 Critical, no zero-days for the first time since June 2024. Two Word RCEs (CVE-2026-40361 and CVE-2026-40364) trigger just by viewing a malicious document in Outlook's Preview Pane and are rated 'Exploitation More Likely.' Windows DNS Client (CVE-2026-41096) lets an attacker-controlled DNS server execute code on any Windows machine resolving a hostile name - echoing SigRed. Other priorities: Netlogon RCE (CVE-2026-41089) and Microsoft SSO Plugin for Jira and Confluence (CVE-2026-41103, CVSS 9.1).
Microsoft disclosed Monday that a phishing campaign between April 14 and 16 hit 35,000+ users across 13,000+ organizations in 26 countries (92% in the US). Lures impersonated internal HR with subjects like 'Internal case log issued under conduct policy.' Each email had a PDF attachment with a 'Review Case Materials' link that walked victims through Cloudflare CAPTCHAs and a final adversary-in-the-middle (AiTM) Microsoft sign-in page. AiTM proxies the real Microsoft login and captures session tokens after MFA - so traditional MFA is bypassed. Healthcare (19%), financial services (18%), and professional services (11%) were the most-targeted sectors.
Anthropic launched Claude Security in public beta yesterday, an enterprise tool that scans code repositories for vulnerabilities, rates each finding's severity and confidence, and generates patch instructions that engineers can apply through Claude Code. The launch is direct response to Mythos and similar AI-driven offensive tools that have been compressing the time between vulnerability disclosure and active exploitation - LiteLLM was exploited 36 hours after disclosure last week, LMDeploy in 13 hours the week before. CrowdStrike, Microsoft Security, Palo Alto Networks, SentinelOne, Trend, and Wiz are integrating Claude Opus 4.7 into their platforms.
CISA added CVE-2026-33825 to its Known Exploited Vulnerabilities catalog on April 23 with a May 7 federal patch deadline. The flaw, nicknamed BlueHammer, is a race condition in Windows Defender's file-remediation logic that lets an unprivileged local attacker overwrite arbitrary files on disk and escalate to SYSTEM on fully-patched Windows 10 and Windows 11 hosts. It was patched in Microsoft's April 8 Patch Tuesday but a working proof-of-concept had already been published to GitHub by a researcher called 'Chaotic Eclipse' on April 7, before the fix shipped. Huntress Labs saw in-the-wild exploitation from April 10, with attackers also picking up two sibling Defender zero-days the same researcher leaked: RedSun (another local privilege escalation) and UnDefend (a denial-of-service that blocks Defender from pulling security definition updates, effectively disarming the EDR). Those two still have no Microsoft patch. The combination - a working privilege-escalation path plus an unpatched technique to silently cripple Defender itself - makes this a priority hunt, not just a priority patch.
Microsoft released out-of-band security updates for a critical ASP.NET Core Data Protection flaw that lets unauthenticated attackers forge authentication cookies and escalate to SYSTEM privileges. The bug (CVE-2026-40372) is a regression introduced in the April 2026 Patch Tuesday: the Microsoft.AspNetCore.DataProtection 10.0.0 through 10.0.6 NuGet packages compute the HMAC validation tag (the cryptographic signature that proves a cookie has not been tampered with) over the wrong bytes of the payload and then discard the hash in some cases. The broken check means attackers can forge payloads that pass DataProtection's authenticity checks and decrypt previously-protected data in auth cookies, antiforgery tokens, TempData, and OIDC state. Microsoft noticed the flaw only after users reported decryption failures in their apps after installing the .NET 10.0.6 update. Critical operational detail: updating to 10.0.7 stops future forgeries, but any tokens an attacker already got the app to legitimately sign during the vulnerable window (session refresh tokens, API keys, password reset links) remain valid forever unless you rotate the DataProtection key ring. Patching alone is not enough.
Shadowserver data shows 1,300+ internet-exposed Microsoft SharePoint servers remain unpatched against CVE-2026-32201, a spoofing flaw Microsoft confirmed as a zero-day and CISA added to its Known Exploited Vulnerabilities catalog the same day the fix dropped in April Patch Tuesday. Fewer than 200 systems have been patched since the update shipped last week. The flaw affects SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition. An unauthenticated attacker can perform network spoofing through improper input validation in a low-complexity attack that needs no user interaction, letting them view sensitive information and modify data, though not affect availability. Microsoft has not described the exploitation technique or attributed the attacks to a specific group, which is unusual for a zero-day and hints at an ongoing investigation. CISA ordered federal agencies to patch by April 28 under Binding Operational Directive 22-01, and given ongoing in-the-wild abuse, private-sector operators should treat that as their own deadline. SharePoint's habit of holding cached Office 365 tokens, SharePoint-signed refresh tokens, and IP on sensitive business processes makes any compromise a serious lateral-movement foothold, not a minor information disclosure.
Microsoft has released out-of-band emergency updates to fix two Windows Server issues introduced by the April 2026 Patch Tuesday updates. First issue: some admins experienced failures installing the KB5082063 security update on Windows Server 2025. Second issue: Patch Tuesday cumulative updates caused Windows servers running domain controller roles to enter restart loops due to crashes of the Local Security Authority Subsystem Service (LSASS). The restart loop can also hit newly-set-up domain controllers or existing ones if the server processes authentication requests very early during startup. The Windows Server 2025 OOB update (KB5091157) addresses both issues. OOB updates for other supported Windows Server versions address only the domain controller restart issue. This is the third consecutive year where April Windows Server patches have caused authentication-related breakage, following similar incidents in 2024 and 2025.
Microsoft has confirmed that the April 2026 cumulative updates (KB5082063 for Windows Server 2025, KB5082142 for Windows Server 2022) are causing LSASS crashes that trigger reboot loops on non-Global Catalog domain controllers in environments using Privileged Access Management (PAM). Affected DCs restart repeatedly, preventing authentication and directory services from functioning, potentially rendering the entire domain unavailable. The issue also occurs when setting up new domain controllers or on existing ones processing authentication requests early in startup. A separate bug causes the April update to fail installation entirely on some Windows Server 2025 systems with error code 0x800F0983. A third issue forces some servers into BitLocker recovery mode due to Secure Boot changes bundled in the update. This is the third consecutive year April Patch Tuesday has broken Windows Server authentication - similar LSASS/domain controller issues hit in April 2024 and April 2025.
A new phishing-as-a-service kit called EvilTokens is being sold on Telegram, turning OAuth device code phishing against Microsoft accounts into a turnkey attack. Victims receive emails with PDFs or HTML files containing QR codes or links to pages impersonating Adobe, DocuSign, or SharePoint. The kit captures Microsoft authentication tokens in real time - bypassing MFA - and gives attackers persistent access for business email compromise. The developer says Gmail and Okta support is coming next.
TrustStrike Labs