Microsoft security advisory – September 2026 monthly rollup (AV26-896) – Update 1
Canada's Cyber Centre relays Microsoft's September 2026 rollup; CISA added exploited zero-days CVE-2026-85880 and CVE-2026-81963 to KEV.
Advisory AV26-896 from the Canadian Centre for Cyber Security summarizes Microsoft's September 2026 monthly security rollup, listing affected products across Windows, Office, .NET, Azure, Exchange and SQL Server. It notes Microsoft confirmed CVE-2026-81963 and CVE-2026-85880 have been exploited. On September 8, 2026, CISA added both CVEs to its Known Exploited Vulnerabilities catalog, and administrators are urged to apply the updates.
Microsoft Plugs Nearly 1,000 Security Holes
Microsoft's September Patch Tuesday fixes a record 974 flaws, including two actively exploited Windows zero-days and critical DNS and Windows Shell bugs.
Microsoft released fixes for 974 vulnerabilities, its largest-ever monthly patch batch, bringing the 2026 total above 2,600. Two zero-day privilege elevation flaws, CVE-2026-81963 and CVE-2026-85880, are being actively exploited. Critical bugs include CVE-2026-69730, an unauthenticated DNS weakness in Windows Server 2012 onward and Windows 10 deemed likely to be exploited, and CVE-2026-69829, a CVSS 9.8 Windows Shell remote code execution flaw requiring no privileges or user interaction. Microsoft and other vendors credit AI-assisted discovery for the growing patch volumes.
Microsoft Plugs Nearly 400 Security Holes
Microsoft's August 2026 Patch Tuesday fixes 398 vulnerabilities, including one flaw already being actively exploited and two publicly disclosed before the update.
Microsoft released August 2026 Patch Tuesday updates fixing at least 398 vulnerabilities in Windows and supported software. One of the flaws is already being actively exploited, and two others were publicly detailed ahead of the patch release. The update is one of the larger monthly releases in recent memory.
Microsoft Patch Tuesday, September 2026 Security Update Review
Microsoft's September 2026 Patch Tuesday fixes 974 vulnerabilities, including 113 critical and two actively exploited Windows privilege escalation flaws.
Microsoft's September 2026 Patch Tuesday fixes 974 vulnerabilities, its largest release ever, including 113 critical and 860 important, covering Windows HTTP.sys, Hyper-V, Entra ID, Exchange Server, Office, DNS, and more. Two zero-days are confirmed exploited in the wild: CVE-2026-81963 (Windows Update Stack EoP) and CVE-2026-85880 (ALPC heap overflow), both letting authenticated attackers gain SYSTEM privileges. Notable criticals include an Entra ID authentication bypass (CVE-2026-62916) and multiple Windows DNS Server and Office remote code execution flaws.
CVE-2026-50522: Microsoft SharePoint Server RCE Vulnerability
CVE-2026-50522 is an unauthenticated .NET deserialization RCE in SharePoint Server Subscription, 2019, and 2016; Microsoft patched it July 14, 2026.
CVE-2026-50522 (CWE-502) lets unauthenticated attackers send crafted serialized .NET payloads to network-accessible SharePoint endpoints, triggering gadget-chain deserialization and remote code execution under the privileged SharePoint service account. It affects SharePoint Server Subscription Edition, SharePoint Server 2019, and SharePoint Server 2016 Enterprise; Microsoft published the advisory on July 14, 2026. The EPSS score is 20.346%, but no public PoC exists and the flaw is not in CISA's KEV catalog at publication. Mitigations include applying Microsoft updates, rotating SharePoint machine keys, enabling AMSI, and restricting internet exposure.
Passkey-themed social engineering leads to identity and cloud compromise
Microsoft tracks ongoing cloud intrusions where passkey-themed helpdesk lures enable AiTM credential theft, MFA persistence, and SharePoint data theft.
Microsoft Security Research is tracking active cloud-based intrusions, observed since May 2026, that begin with helpdesk impersonation calls and SMS lures urging urgent passkey, MFA, or SSO updates. The lures lead to adversary-in-the-middle phishing or device-code authentication flows that capture credentials and session tokens or grant actor access, after which the actors add authentication methods, conduct Microsoft Graph reconnaissance, and download SharePoint and OneDrive content via REST APIs. Phishing domains embed victim organization names as subdomains (e.g., contoso.add-passkey[.]com), are often registered with Nicenic, and go operational within hours. Microsoft advises revoking sessions and removing unauthorized authentication methods for confirmed compromises.
Detect and disrupt AI-themed attacks with Microsoft Defender
Microsoft Threat Intelligence reports criminal campaigns impersonating ChatGPT, Copilot, Claude, and DeepSeek in phishing, AiTM, and malvertising attacks reaching 100,000 emails daily.
Microsoft Threat Intelligence observed a growing set of campaigns that abuse trust in popular AI brands: a ChatGPT-themed phishing campaign sent up to 100,000 emails in one day to steal payment card data, and a Claude-themed campaign used adversary-in-the-middle techniques to harvest credentials and access tokens. Other campaigns included malvertising for a fake AI Windows plugin delivering the Vidar stealer and fraudulent DeepSeek installers distributed via GitHub. Initial access broker Storm-3075 used AI-themed malvertising to distribute payloads for multiple downstream actors, and Microsoft notes the AI services themselves were not compromised. Microsoft also details Defender protections such as Safe Links, Safe Attachments, and attack disruption against these multi-stage lures.
Zero Day Initiative — CVE-2026-33824: Remote Code Execution in Windows ...
ZDI details CVE-2026-33824, a double-free in Windows IKEv2 fragment reassembly enabling unauthenticated remote code execution as SYSTEM on Windows.
Zero Day Initiative published technical analysis of CVE-2026-33824, a double-free in the Windows IKE Extension (ikeext.dll) caused by improper ownership handling of a heap blob pointer during IKEv2 fragment reassembly in IkeReinjectReassembledPacket(). A remote unauthenticated attacker can send a crafted IKE_SA_INIT message with a Security Realm Vendor ID followed by fragmented IKE_AUTH payloads to trigger the double free. Successful exploitation could yield arbitrary code execution under the IKEEXT service context (SYSTEM). ZDI also provided IDS detection guidance correlating the two-packet sequence on UDP ports 500 and 4500.
Impersonating IT support: how threat actors turn a remote session into enterprise-wide access
Microsoft details Teams IT-support impersonation campaigns deploying Node.js implants, AD reconnaissance, and WinRM lateral movement toward domain controllers.
Microsoft Threat Intelligence describes a human-operated campaign where attackers impersonate IT/helpdesk staff via Microsoft Teams external collaboration, talk users into granting remote sessions, and use RMM tools for interactive access. During the session they run PowerShell to silently install a malicious MSI that stages a portable Node.js runtime and obfuscated JavaScript implant for C2, executing follow-on payloads via rundll32. Operators then perform host and Active Directory reconnaissance, capture desktop screenshots, and pivot via WinRM on port 5985 to domain controllers and certificate authorities. The hands-on-keyboard chain, which can precede data theft and ransomware, blends into normal operations by relying on Teams, Quick Assist, msiexec, and Node.js; Microsoft shares hunting and mitigation guidance.
September 2026 Microsoft Patch Tuesday, (Tue, Sep 8th)
Microsoft's September 2026 Patch Tuesday fixes a record 973 vulnerabilities, including 113 critical and two Windows privilege-escalation flaws already exploited in the wild.
Microsoft patched 973 vulnerabilities this month, its largest Patch Tuesday ever and far above the previous record of 664 set in July 2026, with 113 rated critical. Two Important elevation-of-privilege flaws (CVSS 7.8) are confirmed exploited in the wild: CVE-2026-81963 in the Windows Update Stack (improper link resolution, affects Windows 11 and Server 2025) and CVE-2026-85880 in Windows ALPC (heap-based buffer overflow allowing sandbox escape to SYSTEM, affects Windows 10 and Server 2012-2022). Critical unauthenticated RCEs (CVSS 9.8) were also fixed in Skype for Business Server (CVE-2026-66302), Windows Message Queuing (CVE-2026-69579), and Windows RRAS (CVE-2026-69590). SANS urges prioritizing the two exploited EoP fixes, then patching exposed MSMQ, RRAS, and Skype for Business deployments.
Windows Defender ShieldCrash 0-Day Lets Attackers Read Arbitrary Files as SYSTEM
Unpatched Windows Defender zero-day 'ShieldCrash' PoC lets local attackers read arbitrary files as SYSTEM, apparently bypassing the CVE-2026-69414 patch.
Researcher MSNightmare published a skeleton proof-of-concept for 'ShieldCrash', an unpatched Microsoft Defender flaw enabling arbitrary file reads with SYSTEM privileges that reportedly persists on supported Windows versions after September 2026 updates. It appears to bypass the recent fix for the Malware Protection Engine elevation-of-privilege flaw CVE-2026-69414 (ShieldBreak), patched in engine version 1.1.26080.3. SYSTEM-level file disclosure could expose credentials, application secrets and registry hives and support post-compromise reconnaissance. No active exploitation is confirmed and Microsoft had issued no specific patch or mitigation at disclosure time.
Cyber Security News
Microsoft's September Patch Tuesday fixes nearly 1,000 vulnerabilities; CISA warns two of the flaws are being actively exploited.
Microsoft's September 2026 Patch Tuesday release addresses close to 1,000 vulnerabilities, with CISA warning that two of the bugs are being actively exploited. The Record's homepage digest also lists briefs including a US offer of $10 million for information on an Iranian hacker accused of attacking critical infrastructure and a leak of health data on more than 9.5 million people from the Aesto record system. Additional briefs cover a Russian suspect's extradition to the US for bank account takeovers, US-British coordination on scam center takedowns, G7 guidance on quantum cyber threats, a large DDoS attack on Norwegian public services, and Slovenian casinos reopening after a cyberattack.
Nearly 22,000 Microsoft Exchange servers remain exposed to critical security flaw (CVE-2026-62911)
About 22,000 Microsoft Exchange servers remain unpatched against critical auth bypass CVE-2026-62911 as a working exploit circulates online.
CVE-2026-62911 is a critical authentication bypass by capture-replay in Microsoft Exchange Server that allows an authorized attacker to elevate privileges over the network, with a CVSS score of 8.0. Microsoft patched the flaw on August 11, 2026, but Shadowserver Foundation scans show roughly 22,000 servers unpatched, with the US (6,200) and Germany (5,100) leading; BSI reports 85% of on-premises Exchange servers in Germany are still vulnerable. The Netherlands' NCSC-NL flagged that a working exploit is circulating, and Exchange 2016/2019 require the Extended Security Updates program for fixes.
Microsoft’s September 2026 Patch Tuesday addresses 964 CVEs (CVE-2026-81963, CVE-2026-85880)
Microsoft's September 2026 Patch Tuesday fixes a record 964 CVEs, including two zero-days actively exploited in the wild.
Microsoft patched a record 964 CVEs in its September 2026 Patch Tuesday release, with 101 rated critical and 824 rated important, making it the largest Patch Tuesday to date. The release includes fixes for two zero-days that were exploited in the wild, with CVE-2026-81963 and CVE-2026-85880 highlighted in the release. Affected products span Windows core components, Office, Exchange, .NET, Visual Studio, Active Directory services (including AD CS and AD FS) and numerous Azure services. Tenable notes the release surpasses July's as the biggest ever.
Counterfeit installers turn routine software downloads into enterprise breaches
Microsoft warns of a multi-sector campaign using counterfeit download sites for Edge, Kaspersky and Razer to deliver trojanized installers with persistent implants.
Microsoft Defender Experts tracked a campaign breaching organizations in healthcare, manufacturing, gaming, technology, logistics, government, and education via spoofed vendor download pages, often using .com.cn and .hl.cn domains. Installers keep the same filename while their hash changes on every download, indicating server-side payload generation that defeats file-based detection. The chain abuses msiexec.exe and scheduled tasks for persistence, adds Defender exclusions, deletes shadow copies, and disables Windows Update, with some hands-on-keyboard activity. The activity is consistent with the publicly reported Silver Fox (Yinhu) campaign, though Microsoft has not attributed it to a nation-state actor.
Microsoft Patches 398 Flaws Including a Windows Driver Zero
Microsoft's August Patch Tuesday fixes 398 CVEs, including actively exploited Windows zero-day CVE-2026-68820 used by Lazarus for SYSTEM privilege escalation.
Microsoft's August 2026 Patch Tuesday release addresses 398 new vulnerabilities, 62 rated Critical by the Zero Day Initiative, with CVE-2026-68820 (CVSS 7.0), a use-after-free in the afd.sys Windows kernel driver, the only flaw flagged as actively exploited. Check Point Research attributed exploitation of the privilege escalation bug to Lazarus' Operation Dream Job campaign. Four unauthenticated remote code execution flaws rated 9.8 affect Windows DNS Server (CVE-2026-62878, called wormable by ZDI), Windows Deployment Services (CVE-2026-62893), Microsoft QUIC (CVE-2026-62815) and HPC Pack (CVE-2026-59124). The release also completes a two-part SharePoint fix with RCE component CVE-2026-63520, following July's authentication bypass fix CVE-2026-55040.
Risky Bulletin: Russia tells data centers to deploy drone defenses
Russia ordered data center operators to deploy drone strike defenses under a Putin decree allowing temporary state takeover of unprotected critical infrastructure.
The Russian government instructed data center operators to deploy protections against drone strikes under a presidential decree signed by Putin that allows temporary state administration of critical infrastructure operators failing to defend against Ukrainian hacks and drone strikes. Although data centers are not formally critical infrastructure in Russia, the decree applies to them because other sectors depend heavily on cloud services; Russia has more than 180 data centers, over 80% in the European region within range of Ukrainian strikes. The digest also reports a Dropbox breach affecting nearly 5,000 accounts via the Lenovo ID integration, spyware attacks on at least 14 Serbians using NoviSpy or Pegasus, and a password recovery attack targeting hundreds of thousands of X accounts tied to the new X Money service. Other items include a 14-hour compromise of Coder's Cloudflare infrastructure delivering malicious Terraform modules, donor data breaches at Davayte and You Are Not Alone via the Stripe/WooCommerce integration, a $2.5M Aquifer crypto heist, and a TVING breach exposing data of almost 40 million accounts.
Phishing Campaign Sends Millions of Emails Using Invisible Unicode to Evade Filters
Microsoft warns of a high-volume phishing campaign using invisible Unicode characters to split keywords like 'funding' and evade filters, peaking at 2.37 million daily messages.
Microsoft's Security Research team documented a high-volume phishing operation inserting deprecated Unicode Tags characters (U+E0000-U+E007F) inside financial keywords such as 'funding' so literal-string and regex email filters stop matching them. The campaign ran on a weekly cadence with 1-2.37 million weekday messages between February and May 15, 2026, peaking on February 26, 2026. It used hundreds of disposable finance-themed sender domains and relayed mail through ActiveCampaign's click-tracking infrastructure (acemlnd[.]com, activehosted[.]com), lending legitimate platform reputation. Microsoft ties the activity to an AI-assisted SBA loan phishing campaign that Fortra's FIRE team disclosed in September 2025.