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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.

Web discovery (articles for new exploits & KEV entries) · 9d agoVulnerability 3 sourcesCVE-2026-505221

Researchers Disclose AI-Assisted SharePoint Exploit Chain Reaching Unauthenticated RCE

Rapid7 disclosed CVE-2026-55040, a SharePoint JWT validation bypass chaining into CVE-2026-63520 unauthenticated RCE, with research substantially AI-agent-assisted; patches released.

Rapid7 disclosed CVE-2026-55040 (CVSS 9.1), several JWT validation pipeline issues letting unauthenticated attackers impersonate chosen SharePoint users by SID or UPN, chained with CVE-2026-63520 (CVSS 8.1), an unsafe .NET type instantiation in Business Connectivity Services yielding RCE as the service account. An AI agent contributed significantly across 96 sessions and roughly 80,000 tool calls over 24 active days, though an expert had to steer it and it repeatedly overstepped its threat model. No exploitation of the bypass had been reported as of CISA's July 14 assessment. The RCE affects SharePoint Subscription Edition, 2019, and 2016, plus Project Server 2013 SP1 and Office Web Apps 2013 SP1; the July updates break the chain.

The Hacker News · Aug 11, 2026VulnerabilityCVE-2026-55040CVE-2026-635201

SharePoint RCE CVE-2026-45659 Added to CISA KEV After Active Exploitation

CISA adds actively exploited SharePoint RCE CVE-2026-45659 (CVSS 8.8) to KEV; an August 11 update confirms ransomware groups are exploiting the flaw.

CVE-2026-45659 is a deserialization of untrusted data RCE in Microsoft SharePoint Server affecting Subscription Edition, 2019, and 2016, patched by Microsoft in May 2026. An authenticated attacker with at least Site Member permissions can execute code remotely over the network. CISA added the flaw to its KEV catalog on July 2 with a July 4 deadline for federal agencies, and on August 11 confirmed ransomware groups are exploiting it. Microsoft separately described Storm-2603 (Warlock ransomware) and an unrelated actor co-existing in one network, with initial access likely via the Gladinet Triofox flaw CVE-2025-11371 (CVSS 9.1).

The Hacker News · Aug 12, 2026Exploit / PoC in the wildCVE-2026-45659CVE-2025-113711

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.

Canadian Centre for Cyber Security · 8d agoAdvisory in the wildCVE-2026-81963CVE-2026-858801

September 2026 Patch Tuesday: Record patch count, 2 zero-days, and a SigRed successor

Microsoft's September 2026 Patch Tuesday delivers a record patch count, fixing two exploited zero-days and a wormable DNS flaw dubbed a SigRed successor.

Microsoft's September 2026 Patch Tuesday sets another record patch count, fixing two vulnerabilities exploited as zero-days: CVE-2026-81963, a Windows Update Stack low-privilege-to-SYSTEM escalation reported by MSTIC, and CVE-2026-85880, a Windows Advanced Local Procedure Call escalation reported by Proofpoint. Zero Day Initiative's Dustin Childs urges priority on a cluster of 20 potentially wormable bugs including DNS RCE CVE-2026-69730, described as a spiritual successor to SigRed, plus Kerberos authentication bypass CVE-2026-69676 that could give any authenticated domain user RCE on domain controllers, and Exchange RCE CVE-2026-55007 via a malicious Visio attachment. All Windows fixes are bundled in cumulative updates, and experts stress prioritizing exploitable, reachable flaws over raw patch counts.

Help Net Security · 7d agoAdvisory in the wildCVE-2026-81963CVE-2026-85880CVE-2026-69730+4 CVEs

Patch Tuesday - September 2026

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.

Rapid7 Blog · 8d agoVulnerability in the wildCVE-2026-85880CVE-2026-81963CVE-2026-85046+10 CVEs

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.

SANS Internet Storm Center · 8d agoVulnerability in the wildCVE-2026-81963CVE-2026-85880CVE-2026-66302+5 CVEs1