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2026-009: Critical Vulnerabilities in Microsoft SharePoint ↗ source

July 23, 2026 CERT-EU Advisory

Summary

On 20 July 2026, WatchTowr identified a proof-of-concept exploit code and subsequently observed active exploitation of CVE-2026-50522 [2], a vulnerability part of an ongoing series of actively exploited flaws [3] affecting on-premise SharePoint Server instances, including CVE-2026-32201, CVE2026-45659, 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. [UPDATED] The vulnerability CVE-2026-50522 (CVSS: 9.8) is a critical deserialisation vulnerability in Microsoft SharePoint that allows a remote attacker to execute arbitrary code on affected systems. While Microsoft indicates that exploitation requires some level of authentication [1], recent findings suggest this may not be the case [2, 4]. [NEW] Over the past month, Microsoft also fixed the following vulnerabilities affecting Microsoft SharePoint Server: unauthorised user (CVSS: 6.5) [5]. Fixed in July 2026. [UPDATED] The vulnerability CVE-2026-50522 affects the following Microsoft SharePoint products. Refer to the respective Microsoft advisories [5–8] for the full list of affected products for the other vulnerabilities.

News Coverage

Articles from the monitored vendor research blogs and security news feeds that reference a CVE cited in this publication, or name the campaign it covers. Coverage begins when feed monitoring started; earlier articles are not indexed.

CVEs Referenced in This Publication

CVECVSSAffected
CVE-2026-50522 9.8 Critical Microsoft SharePoint Microsoft SharePoint contains a deserialization of untrusted data vulnerability which could allow an unauthorized attacker to execute code over a net…
CVE-2026-58644 9.8 Critical Microsoft SharePoint Microsoft SharePoint contains a deserialization of untrusted data vulnerability that allows an unauthorized attacker to execute code over a network.
CVE-2026-45659 8.8 High Microsoft SharePoint Server Microsoft SharePoint Server contains a deserialization of untrusted data vulnerability which allows an authorized attacker to execute code over a net…
CVE-2026-32201 6.5 Medium Microsoft SharePoint Server Microsoft SharePoint Server contains an improper input validation vulnerability that allows an unauthorized attacker to perform spoofing over a netwo…
CVE-2026-56164 5.3 Medium Microsoft SharePoint Server Microsoft SharePoint contains a missing authentication for critical function vulnerability that allows an unauthorized attacker to elevate privileges…

Extracted from the publication text. Each CVE links to its tracked detail page.

Vendors Named in This Publication

Each vendor links to its Known Exploited Vulnerabilities catalog page. Only vendors that appear in the KEV catalog are listed, either because the publication cites one of their KEV entries or because it names them directly.