Microsoft May 2020 Patch Tuesday fixes 111 flaws, 13 Critical
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Microsoft Releases Urgent Patch for SharePoint RCE Flaw Exploited in Ongoing Cyber Attacks
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2026-009: Critical Vulnerabilities in Microsoft SharePoint
WatchTowr observed active exploitation of SharePoint RCE CVE-2026-50522 (CVSS 9.8), part of an ongoing wave of exploited on-prem SharePoint flaws patched by Microsoft.
On 14 July 2026 Microsoft released updates for critical SharePoint Server RCE flaws, including CVE-2026-50522 (CVSS 9.8), a deserialisation vulnerability possibly exploitable without authentication. On 20 July 2026 WatchTowr published PoC exploit code and observed active exploitation of CVE-2026-50522, prompting CISA to urge SharePoint hardening. The advisory also covers recently fixed SharePoint flaws: CVE-2026-32201 (6.5, spoofing), CVE-2026-45659 (8.8, authenticated RCE), CVE-2026-56164 (9.8, unauthenticated privilege escalation), and CVE-2026-58644 (9.8, unauthenticated RCE). Affected products include SharePoint Server Subscription Edition, 2019, and Enterprise Server 2016; CERT-EU recommends immediate patching, credential rotation, and compromise assessments.
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Microsoft SharePoint servers under attack via zero-day vulnerability (CVE-2025-53770)
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U.S. CISA urges to immediately patch Microsoft SharePoint flaw adding it to its Known Exploited Vulnerabilities catalog
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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.
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CVE-2026-50522: Patch Critical SharePoint RCE Now
Microsoft patched CVE-2026-50522 (CVSS 9.8), an unauthenticated deserialization RCE in on-premises SharePoint servers, in its July 2026 updates; no exploitation confirmed at disclosure.
CVE-2026-50522 is a critical (CVSS 9.8) deserialization of untrusted data flaw (CWE-502) allowing unauthenticated remote code execution on on-premises Microsoft SharePoint servers. It affects SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition, with fixes shipped in Microsoft's July 14, 2026 security updates; SharePoint Online is not listed as affected. No public evidence of active exploitation of this specific CVE existed at disclosure, though CISA's SSVC judged the attack automatable with total technical impact.
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U.S. CISA adds Apple macOS, Microsoft SharePoint, Broadcom VMware vCenter, and Microsoft IKE flaws to its Known Exploited Vulnerabilities catalog
CISA adds actively exploited flaws in Microsoft IKE, SharePoint, VMware vCenter, and macOS Screen Sharing to KEV catalog, due August 21.
CISA added four vulnerabilities to its Known Exploited Vulnerabilities catalog: CVE-2026-33824 (Windows IKE remote code execution, CVSS 9.8), CVE-2026-55040 (SharePoint JWT authentication bypass, CVSS 9.1), CVE-2026-59310 (VMware vCenter Syslog path traversal, CVSS 9.8), and CVE-2026-65400 (macOS Screen Sharing improper authentication). The SharePoint flaw combines four weaknesses including alg:none JWT forging to impersonate any user, with Defused researchers observing attackers using Rapid7's PoC against honeypots. The Dutch NCSC confirmed active exploitation of the macOS Screen Sharing flaw on August 15, 2026. Federal agencies must patch by August 21, 2026.
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CVE-2026-63520: Microsoft SharePoint Remote Code Execution (FIXED)
Rapid7 and Microsoft disclose CVE-2026-63520, a SharePoint RCE that chains with CVE-2026-55040 for unauthenticated RCE; patches released.
Rapid7 Labs' zero-day research project on Microsoft SharePoint uncovered two vulnerabilities that, when chained, achieve unauthenticated remote code execution. The second flaw in the chain, CVE-2026-63520, affects all supported versions of Microsoft SharePoint and has been disclosed and fixed. The first chain component, CVE-2026-55040, was disclosed by Rapid7 and Microsoft the previous month.
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Microsoft February 2021 Patch Tuesday fixes 56 bugs, including an actively exploited Windows zero
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CISA adds Microsoft SharePoint bug disclosed at Pwn2Own to its Known Exploited Vulnerabilities catalog
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ToolShell: a story of five vulnerabilities in Microsoft SharePoint
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Public PoC triggers active exploitation of critical SharePoint RCE vulnerability CVE-2026
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Rapid7 Analysis: Microsoft SharePoint Remote Code Execution (CVE-2026-63520)
Rapid7 published technical analysis of CVE-2026-63520, a remote code execution vulnerability in Microsoft SharePoint.
Rapid7 released an analysis covering CVE-2026-63520, a remote code execution flaw affecting Microsoft SharePoint. SharePoint is widely deployed in enterprise environments, making exposed, unpatched servers a likely target for exploitation. Defenders should consult the Rapid7 write-up for exposure checks and patch guidance. The available text does not confirm active exploitation at this time.
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2026-004: Critical Vulnerability in SharePoint Exploited
CVE-2026-20963 (CVSS 9.8), an unauthenticated RCE in on-prem SharePoint, was added to CISA's KEV on 18 March 2026 and is actively exploited.
CERT-EU warns about CVE-2026-20963, a CVSS 9.8 unauthenticated remote code execution flaw in SharePoint caused by deserialisation of untrusted data, affecting SharePoint Server Subscription Edition, 2019, and Enterprise Server 2016. Microsoft raised the CVSS score on 17 March 2026 and the flaw entered CISA's Known Exploited Vulnerabilities catalogue on 18 March 2026. Three additional SharePoint RCE flaws (CVE-2026-26106, CVE-2026-26113, CVE-2026-26114) were fixed in the March 2026 release. CERT-EU urges immediate patching of internet-facing servers plus AMSI Full Mode, EDR deployment, ASP.NET machine key rotation, and compromise assessments.
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Microsoft issues emergency patches for SharePoint zero
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Microsoft January 2019 Patch Tuesday updates fix 7 critical vulnerabilities
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