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On 17 March 2026, Microsoft updated one of its January 2026 security advisories related to a remote code execution vulnerability in Microsoft SharePoint. Specifically, Microsoft raised the CVSS score and changed the FAQ section to indicate that the vulnerability could be exploited by an unauthenticated attacker. This vulnerability was added in the CISA's Known Exploited Vulnerabilities (KEV) catalogue on 18 March 2026. Additionally, three further RCE flaws affecting Microsoft SharePoint were addressed in the March 2026 release. CERT-EU strongly recommends updating SharePoint servers as soon as possible, prioritising internet-facing assets. CERT-EU also encourages IT administrators to take necessary remediation actions.

[UPDATED] On 14 July 2026, Microsoft released security updates addressing critical remote code execution (RCE) vulnerabilities in Microsoft SharePoint Server. On 20 July 2026, WatchTowr identified a proof-of-concept exploit code and subsequently observed active exploitation of CVE-2026-50522, a vulnerability part of an ongoing series of actively exploited flaws affecting on-premise SharePoint Server instances, including CVE-2026-32201, CVE-2026-45659, CVE-2026-56164, and CVE-2026-58644. CERT-EU strongly recommends updating affected servers immediately, rotating credentials for any assets that may have been exposed to the internet, and conducting a compromise assessment.

Microsoft is publishing 421 vulnerabilities on August 2026 Patch Tuesday , including 236 vulnerabilities in Windows. This is lower volume than last month’s record-breaking behemoth, but still one of the largest Patch Tuesday totals ever. There is no reason to suppose that Patch Tuesday will ever return to the lower volumes we saw prior to 2026. Microsoft is aware of exploitation in the wild for one of the vulnerabilities published today, as well as public disclosure for two others, although the Notable CVEs section of the Security Update Guide omits one of these. As usual, browser vulns are not included in the Patch Tuesday count above, but unusually, Microsoft does not appear to have published any desktop browser security patches so far this month. SharePoint: critical RCE chain by Rapid7 Today sees the publication of CVE-2026-63520 , a high-severity remote code execution in Microsoft SharePoint. Discovered by Rapid7 Senior Principal Security Researcher Stephen Fewer , and published today in coordination with Microsoft; this vulnerability is the second in a pair of exploits which, when chained together, comprise a critical unauthenticated remote code execution vulnerability in a v

Overview On July 14, 2026, Rapid7 and Microsoft disclosed CVE-2026-55040, an authentication bypass vulnerability affecting Microsoft SharePoint. Today we are publishing a technical analysis of the vulnerability along with an accompanying proof-of-concept (PoC) script . Figure 1: The Rapid7 Labs PoC for CVE-2026-55040. ⠀ A remote unauthenticated attacker can leverage CVE-2026-55040 to bypass authentication on a vulnerable SharePoint server, and perform operations as a SharePoint site user or administrator. The vulnerability is due to several issues in the JWT token validation pipeline. Analysis The following technical analysis is based upon SharePoint Server Subscription Edition version 16.0.19725.20210 . A critical authentication bypass vulnerability exists in SharePoint Server Subscription Edition's JWT token validation pipeline. The root cause is a chain of four distinct weaknesses that, when combined, allow an unauthenticated remote attacker to forge a valid JWT and impersonate any SharePoint site user. The below analysis is based upon decompilation and code review of the Microsoft.SharePoint.IdentityModel module from a fully patched SharePoint Server Subscription Edition instan

Overview Rapid7 Labs conducted a zero-day research project against Microsoft SharePoint, resulting in the discovery of two new vulnerabilities that, when chained together, achieve unauthenticated remote code execution (RCE) against a vulnerable SharePoint server. Today, both Rapid7 and Microsoft are disclosing the second vulnerability in this chain, the RCE vulnerability CVE-2026-63520. The first vulnerability in the chain, CVE-2026-55040, was disclosed by Rapid7 and Microsoft last month. Our full disclosure timeline for the exploit chain can be seen below in Figure 1. Figure 1: The road to disclosure. ⠀ CVE-2026-63520 affects all supported versions of Microsoft SharePoint. An attacker can leverage CVE-2026-63520 to execute arbitrary code on a vulnerable SharePoint server with the privileges of the SharePoint Site’s service account. The vulnerability is due to an unsafe .NET type instantiation issue within the Business Connectivity Services . CVE-2026-63520 has a CVSSv3.1 score of 8.1 (High) , and a Common Weakness Enumeration (CWE) of CWE-20: Improper Input Validation . While the severity of the RCE is described as high, chained together with CVE-2026-55040 it becomes part of a cr