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.
September 2026 Patch Tuesday forecast expects record CVE volume after August's 398 fixes, with SharePoint flaws CVE-2026-55040 and CVE-2026-63520 actively exploited.
This Patch Tuesday forecast column notes August 2026 Patch Tuesday was the second largest ever with 398 resolved CVEs, yet only one was confirmed actively exploited. SharePoint flaws CVE-2026-55040 and CVE-2026-63520 are being chained for authentication bypass and remote code execution in active attacks against unpatched servers. Microsoft Defender's ShieldBreak elevation of privilege flaw (CVE-2026-69414) is publicly disclosed with PoC code and a fix is expected, while Chrome CVE-2026-85046 was reported exploited in the wild. Several products, including Windows 11 24H2 Home/Pro and Exchange Server 2016/2019 ESU, reach end of support in October 2026.
Microsoft's record September 2026 Patch Tuesday fixes 974 CVEs, including two exploited Windows privilege-escalation zero-days and 20 wormable bugs.
Microsoft's September 2026 Patch Tuesday fixes a record 974 CVEs, including two actively exploited zero-days: CVE-2026-85880, an ALPC heap buffer overflow, and CVE-2026-81963 in the Windows Update Stack, both CVSS 7.8 local privilege escalations. It also addresses an unauthenticated Exchange RCE (CVE-2026-55007) triggered by Visio attachment content indexing under memory pressure, an RDP use-after-free (CVE-2026-69525, CVSS 9.8), and 20 wormable flaws in DNS, DHCP, SMB, Active Directory, and other components. ZDI attributed the rising volume partly to AI-assisted vulnerability discovery, noting no corresponding spike in active exploits yet.
Microsoft's record 974-CVE Patch Tuesday ships two exploited Windows zero-days, while Adobe's StyleSmuggler zero-day (CVE-2026-75650) gives unauthenticated RCE in Magento.
Microsoft's September Patch Tuesday addresses 974 CVEs, including two zero-days already under exploitation: CVE-2026-85880, a Windows ALPC privilege escalation leading to SYSTEM via sandbox escape, and CVE-2026-81963, a Windows Update Stack privilege escalation. Adobe patched 172 CVEs, including the max-severity StyleSmuggler zero-day CVE-2026-75650 in Magento and Adobe Commerce, which Sansec reports is being exploited since September 4 to inject PHP into templates and install a C2-connected backdoor. CISA added CVE-2026-85880, CVE-2026-81963, and CVE-2026-75650 to its Known Exploited Vulnerabilities Catalog with patch deadlines of September 22 and September 11. The piece also notes Google-patched Chrome V8 zero-day CVE-2026-85046 lacks a Microsoft advisory for Edge, and flags nine Exchange Server flaws including remote unauthenticated RCE CVE-2026-55007.
Microsoft's September 2026 Patch Tuesday fixes 999 CVEs, a record, with two zero-day privilege escalation flaws already exploited in the wild.
Microsoft published 974 own-product vulnerabilities plus 25 non-Microsoft CVEs, totaling 999 — the most CVEs Microsoft has ever released in a single day. Two flaws are exploited in the wild: CVE-2026-85880, an out-of-bounds write in Windows ALPC granting SYSTEM privileges, and CVE-2026-81963, an improper link resolution flaw in the Windows Update Stack also leading to SYSTEM. Chrome's V8 zero-day CVE-2026-85046 was patched in Edge on September 2, but Microsoft had not published a corresponding advisory, leaving uncertainty about other Chromium fixes in Edge. October 14 lifecycle changes end servicing for Windows 11 24H2 Home/Pro, Office 2021, and Exchange Server 2016/2019.
Microsoft's September 2026 Patch Tuesday fixes a record 974 CVEs, including two Windows zero-days exploited in the wild for privilege escalation.
Microsoft patched 974 vulnerabilities, its largest Patch Tuesday ever, including CVE-2026-85880, a heap buffer overflow in Windows ALPC allowing AppContainer sandbox escape to System, and CVE-2026-81963, a link-following flaw in the Windows Update Stack enabling local privilege escalation. Both were exploited as zero-days before the patch. ZDI's Dustin Childs says 20 of the fixed flaws are wormable, enabling unauthenticated remote code execution. The release also covers 723 Windows flaws and 222 Office bugs, plus fixes in Exchange, SharePoint, SQL Server, Azure and Exchange Server RCE (CVE-2026-55007).
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's September 2026 Patch Tuesday fixes 974 vulnerabilities across Windows and Office, including two actively exploited Windows privilege-escalation zero-days.
Microsoft's September 2026 Patch Tuesday addresses 974 vulnerabilities spanning Windows, Office, SQL Server, SharePoint, Exchange, Azure, and developer tools. Two Windows zero-days are confirmed exploited in attacks: CVE-2026-85880, a Windows ALPC elevation-of-privilege flaw, and CVE-2026-81963, a Windows Update Stack privilege-escalation flaw involving link following. The release also includes Critical fixes for Windows Secure Kernel Mode, VBS Enclave, Excel, and Word.
High-severity authentication bypass CVE-2026-62911 in Exchange Server has public exploit code; about 22,000 servers remain unpatched and internet-exposed.
Microsoft's August 2026 Patch Tuesday fixed CVE-2026-62911 (CVSS 8.0), an authentication bypass affecting Exchange Server 2016, 2019 and Subscription Edition. Successful exploitation lets an attacker with basic privileges take over all mailboxes on the targeted server, including reading and sending email and downloading attachments. As of September 1, Shadowserver identified roughly 22,000 unpatched, internet-exposed Exchange servers, including about 6,200 in the US and 5,100 in Germany. NCSC-NL confirmed working exploit code is publicly available, while CISA has not yet reported exploitation in the wild.
August 2026 Patch Tuesday forecast urges risk-based triage as AI inflates CVE volume, flags actively exploited SharePoint RCE CVE-2026-50522 and LegacyHive Windows flaw.
July 2026 Patch Tuesday set records with over 600 CVEs, including 405 for Windows 11 and Server 2025, though only two were exploited zero-days and one was publicly disclosed. The author recommends prioritizing known-exploited and internet-facing vulnerabilities, matching patches to high-risk systems, and accelerating ring-based deployment toward Microsoft's suggested three-day turnaround. Notable items include actively exploited SharePoint RCE CVE-2026-50522 enabling machine key theft, the unassigned LegacyHive Windows User Profile Service flaw, and several end-of-servicing dates for Windows and Exchange.
Alloy Taurus (GALLIUM) compromised Southeast Asian government networks from 2022 to 2023 using Exchange web shells and undocumented .NET backdoors Reshell and Zapoa.
Unit 42 tracked persistent multiwave intrusions at a Southeast Asian government starting in early 2022 and continuing through 2023, attributing the activity with moderate confidence to Alloy Taurus (aka GALLIUM), a Chinese state-aligned espionage group. Attackers exploited Exchange Server vulnerabilities to deploy web shells including China Chopper, then ran reconnaissance with Fscan and WebScan, created administrative accounts, and installed undocumented .NET backdoors named Reshell and Zapoa. They established resilience by installing SoftEther VPN, brute-forced Active Directory credentials with Kerbrute, and dumped credential stores with GoDumpLsass and LsassUnhooker. The campaign reflects long-term espionage tradecraft to maintain a foothold.
Local Privilege Escalation via Link Following in Windows Update Stack
CVE-2026-81963 is a link-following flaw (CWE-59, improper link resolution before file access) in the Microsoft Windows Update Stack, in which the component fails to correctly resolve file links before opening them. A local attacker with low privileges can plant or manipulate a link (symlink/junction) that the privileged update stack follows during operation, redirecting its file access to an attacker-controlled target. The result is local privilege escalation — CVSS 3.1 rates this 7.8 (high) with high confidentiality, integrity, and availability impact — allowing an authorized local user or malware already on the machine to gain elevated rights. Affected products are Windows 11 23H2, 24H2, 25H2, and 26H1 and Windows Server 2025; any unpatched system on those versions is exposed to any local account holder. The flaw was fixed in Microsoft's record September 2026 Patch Tuesday (974 CVEs), was added to CISA's KEV on 2026-09-08 as one of two Windows zero-days reported as exploited in the wild, and has no known public PoC or confirmed ransomware use.
· Microsoft Windows 11 23H2, 24H2, 25H2, 26H1 · Microsoft Windows Server 2025 KEVmass
Heap-Based Buffer Overflow in Windows ALPC Enables Local Privilege Escalation
CVE-2026-85880 is a heap-based buffer overflow in Windows Advanced Local Procedure Call (ALPC), the Windows mechanism for local inter-process communication. An authorized local attacker can trigger the overflow by submitting crafted input over ALPC, corrupting heap memory in the component that handles the request. Successful exploitation allows the attacker to execute code with elevated privileges, typically gaining SYSTEM-level control of the local host, which is especially valuable as a post-exploitation or sandbox-escape step. Affected products include Windows 10 (1607, 1809, 21H2, 22H2) and Windows Server 2012, 2016, 2019, and 2022, meaning most on-premises Windows estates are in scope. The flaw was fixed in Microsoft's record 974-CVE September 2026 Patch Tuesday and was added to CISA's KEV on 2026-09-08, confirming exploitation in the wild; press reports describe Windows zero-days being chained with a Chrome zero-day in 'BlueMoon' kit attacks, though the data does not explicitly confirm this CVE is the Windows flaw in that chain.
· Microsoft Windows 10 1607, 1809, 21H2, 22H2 · Microsoft Windows Server 2012, 2016, 2019, 2022 KEVmass
Actively Exploited V8 Type Confusion in Google Chrome (CVE-2026-85046)
Google Chrome versions prior to 152.0.7977.82 contain a type confusion flaw (CWE-843) in the V8 JavaScript engine, which mishandles object types during engine operations (public proof-of-concept writeups indicate it is reachable through array sorting and WebAssembly-related code paths). A remote attacker triggers the flaw simply by getting a user to open a crafted HTML page, with no privileges or authentication required. Successful exploitation lets the attacker execute arbitrary code inside the browser's sandbox, and public reporting shows it being chained with Windows zero-days (the 'BlueMoon' exploit kit) by Chinese espionage groups for broader compromise. Any user of an unpatched Chrome or another build embedding the affected V8 engine is exposed. The vulnerability is a zero-day that was actively exploited in the wild before patching, was added to CISA's KEV on 2026-09-04, and has five public proof-of-concept references.
· Google Chrome prior to 152.0.7977.82 · Google Chromium V8 V8 engine versions bundled with Chrome prior to 152.0.7977.82 KEV PoC ×5mass
Double Free Enables Unauthenticated RCE in Microsoft Exchange Server
CVE-2026-55007 is a double-free memory corruption flaw (CWE-415) in Microsoft Exchange Server in which the same heap allocation is freed twice, corrupting memory. A remote, unauthenticated attacker can trigger the flaw over the network, though the high attack complexity (AC:H) means reliable exploitation likely depends on favorable heap/timing conditions, making it harder to weaponize than typical pre-auth RCEs. Successful exploitation yields arbitrary code execution with high impact on confidentiality, integrity, and availability (CVSS 3.1: 8.1). Any organization running on-premises Microsoft Exchange Server is in scope, with the greatest risk on servers reachable from untrusted networks. As of now there is no public proof-of-concept, the flaw is not in CISA's KEV catalog, and EPSS estimates only a 0.7% chance of exploitation within 30 days; it was disclosed amid Microsoft's record September 2026 Patch Tuesday (974 CVEs), which press coverage highlighted for notable Exchange flaws.
Missing Authorization in Microsoft Entra ID Enables Privilege Escalation
CVE-2026-83941 is a missing-authorization flaw (CWE-862) in Microsoft Entra ID, the cloud identity service behind Microsoft 365 and Azure. An already-authenticated, low-privileged user can send a network request to an Entra ID endpoint that fails to enforce proper authorization checks, requiring no user interaction. Exploitation lets the attacker elevate their privileges within the directory, with high confidentiality and integrity impact (CVSS 9.9, scope changed). Any organization that uses Microsoft Entra ID is in the affected population. The flaw was patched in Microsoft's September 2026 Patch Tuesday release; it is not in CISA KEV, has no known public proof-of-concept, and carries a low EPSS of roughly 0.7%.
Use-After-Free RCE in Windows Remote Desktop Services
CVE-2026-69525 is a use-after-free memory corruption flaw (CWE-416) in Windows Remote Desktop Services, rated critical at CVSS 9.8. Per the CVSS vector, a remote, unauthenticated attacker can reach the vulnerable code path over the network with no privileges and no user interaction, presumably by sending crafted input to the RDP/RDS service. Successful exploitation yields remote code execution with high impact on confidentiality, integrity, and availability. Any Windows system running Remote Desktop Services is affected, and organizations exposing RDP (TCP 3389) to the internet are the primary concern, since public scans show millions of such endpoints. There is no public proof-of-concept or CISA KEV listing yet, and EPSS estimates a ~1.1% (63rd percentile) chance of exploitation within 30 days; the fix shipped as part of Microsoft's record 974-CVE Patch Tuesday, which separately included two exploited Windows zero-days and 20 wormable bugs.
CVE-2026-69730 is a use-after-free memory corruption flaw (CWE-416) in the Windows DNS service that allows an unauthenticated, remote attacker to execute arbitrary code by sending crafted network traffic to the affected system. Because the flaw is network-exploitable with no privileges or user interaction required (CVSS 3.1 9.8), any system running the vulnerable DNS service is a direct target. Successful exploitation would give the attacker code execution in the context of the DNS service, which on Windows Server typically runs with high privileges such as SYSTEM, and could enable wormable spread between vulnerable hosts. Affected organizations are those running the Windows DNS Server role — a component deployed on virtually all Windows Server domain controllers and on dedicated Windows DNS servers, especially those exposed to untrusted networks. As of the September 2026 Patch Tuesday release, there is no known public proof-of-concept, the flaw is not listed in CISA's KEV, and it has not been confirmed exploited in the wild, though it was flagged among roughly 20 'wormable' bugs and described in press coverage as a successor to the 2020 SigRed Windows DNS RCE.
· Microsoft Windows DNS Server role (Windows Server)mass
Capture-Replay Authentication Bypass in Microsoft Exchange Server
Microsoft Exchange Server contains an authentication bypass flaw (CWE-294) in which captured authentication material can be replayed, allowing an authorized attacker to elevate privileges over a network. Per the CVSS vector, the attack is network-based with low complexity but requires the attacker to already hold low privileges and some user interaction, and success yields high impact on confidentiality, integrity, and availability. Affected products include on-premises Exchange Server and Exchange Server Subscription Edition, though specific vulnerable version ranges are not specified in the available data. Public scans indicate nearly 22,000 Exchange servers remain exposed to the flaw following the August 2026 Patch Tuesday fixes. No in-the-wild exploitation, public proof-of-concept, or KEV listing is known; the bug was demonstrated at Pwn2Own (ZDI-26-534) and carries an EPSS estimate of 1.3% probability of exploitation within 30 days.
· microsoft exchange server · microsoft exchange server subscription editionlarge
Heap Buffer Overflow in Microsoft Excel Allows Local Code Execution (CVE-2026-81959)
CVE-2026-81959 is a heap-based buffer overflow (CWE-122) in Microsoft Office Excel, with an associated integer overflow/wraparound (CWE-190) that Microsoft notes as part of the flaw. Because the attack vector is local and requires user interaction, exploitation requires a user to open a specially crafted spreadsheet file in an affected Excel or Office installation, for example one delivered via email or downloaded from an untrusted source. Successful exploitation allows an unauthorized attacker to execute arbitrary code in the context of the current user, with high impact on confidentiality, integrity, and availability on the victim machine. Anyone running Excel in Microsoft 365 Apps or perpetual Office 2016, 2019, 2021, or 2024 is affected. The flaw was addressed in Microsoft's September 2026 Patch Tuesday (a release covering 974 vulnerabilities); it is not in CISA KEV, no public proof-of-concept is known, and EPSS puts 30-day exploitation probability at just 0.4%, so no confirmed in-the-wild exploitation is known.
Capture-replay authentication bypass in Microsoft MSAL for Node.js
CVE-2026-84003 is an authentication bypass by capture-replay (CWE-294) in the Microsoft Authentication Library (MSAL) for Node.js, the library Node.js applications use to authenticate users and services against Microsoft's identity platform. An attacker positioned on the network who can capture authentication material in transit can replay it to authenticate as a legitimate user or client, with no privileges or user interaction required; the high attack complexity reflects the difficulty of intercepting and replaying the exchange while it remains valid. Successful exploitation enables spoofing with high impact on confidentiality and integrity (the attacker can act as the victim), though there is no availability impact. Any organization running Node.js server applications, APIs, daemons, or CLIs that depend on MSAL for Node.js is affected, with end users of those applications exposed through them. As of this writing there is no known public proof-of-concept, the flaw is not in CISA KEV, and EPSS puts the 30-day exploitation probability at 0.4% (37th percentile); the fix shipped in Microsoft's September 2026 Patch Tuesday.
· Microsoft Authentication Library (MSAL) for Node.js (@azure/msal-node)mass
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