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CISA and Microsoft warned that multiple on-premises SharePoint Server vulnerabilities are being actively exploited against internet-facing systems, with attackers using a chain involving CVE-2026-32201, CVE-2026-45659, and CVE-2026-56164 to gain unauthorized access, execute code, steal IIS and ASP.NET machine keys, maintain persistence, and deploy malware. The agencies said the activity affects supported on-premises SharePoint deployments rather than SharePoint Online, and follows earlier Microsoft reporting that Chinese threat actors including Linen Typhoon, Violet Typhoon, and Storm-2603 had abused similar SharePoint flaws to install web shells, dump credentials, move laterally, and in some cases deploy Warlock ransomware.
Microsoft’s July 2026 updates also fixed two additional critical SharePoint bugs, CVE-2026-55040 and CVE-2026-58644, which were not yet confirmed as exploited but were assessed as likely targets for rapid weaponization, while separate reporting said another SharePoint exploit chain may remain unpatched pending a later release. Defenders were urged to immediately apply available patches, enable AMSI in Full Mode, reduce or remove internet exposure, restrict access to SharePoint Central Administration, review logs and endpoint telemetry for compromise, and only rotate IIS or ASP.NET machine keys after confirming whether intrusion activity is already present.
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4 events from the most recent confirmed update back to the earliest known activity.
The Canadian Centre for Cyber Security issued Alert AL26-017 warning that CVE-2026-56164, CVE-2026-55040, and CVE-2026-58644 affect on-premises Microsoft SharePoint Server. The alert urged organizations to patch, monitor for compromise, and reduce internet exposure, while noting active exploitation of CVE-2026-56164 and related SharePoint flaws.
CISA warned that CVE-2026-32201, CVE-2026-45659, and CVE-2026-56164 were under active exploitation against internet-exposed on-premises SharePoint servers. The agency said attackers were stealing IIS machine keys and using deserialization for persistence and malware deployment, while urging hardening and patching.
Microsoft disclosed CVE-2026-55040 and CVE-2026-58644 in on-premises SharePoint Server and issued July 2026 Patch Tuesday updates for SharePoint Server 2016, 2019, and Subscription Edition. Beazley noted Rapid7 had reported a separate SharePoint exploit chain remained unpatched pending an expected August release.
Microsoft said multiple on-premises SharePoint Server vulnerabilities were being actively exploited and attributed observed activity to Linen Typhoon, Violet Typhoon, and Storm-2603. The company described post-exploitation behavior including web shell deployment, ASP.NET MachineKey theft, credential dumping, lateral movement, and Warlock ransomware distribution.
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More than **1,370 internet-facing Microsoft SharePoint servers** were reported exposed to active exploitation of **`CVE-2026-32201`**, a spoofing vulnerability affecting SharePoint Server 2016, 2019, and Subscription Edition. Microsoft disclosed the flaw in April and CISA added it to the **Known Exploited Vulnerabilities** catalog the same day, underscoring the urgency for defenders. Although Microsoft scored the bug at **CVSS 6.5**, the risk is elevated because it can be exploited **remotely without authentication** against exposed on-premises deployments, potentially allowing attackers to impersonate users, access or alter sensitive content, steal credentials, and move laterally inside victim environments. The exposure comes amid broader concern over SharePoint security, including Microsoft's disclosure of **`CVE-2026-26106`**, a **remote code execution** vulnerability in SharePoint Server, and earlier reporting that a **China-linked threat actor** was involved in SharePoint attacks, according to Mandiant. The concentration of exposed systems was highest in the **United States**, and the combined reporting points to sustained attacker interest in SharePoint as a route into enterprise networks. Organizations were urged to apply Microsoft's available updates, reduce direct internet exposure of SharePoint servers, and closely monitor authentication and document-access activity for signs of compromise.
Jun 29, 2026
CISA added **`CVE-2026-45659`** to its Known Exploited Vulnerabilities catalog after confirming active attacks against Microsoft SharePoint Server. The high-severity flaw is a **deserialization of untrusted data** issue that lets an authenticated attacker with only **Site Member** permissions execute arbitrary code on vulnerable, internet-exposed servers, with no user interaction required and low attack complexity. Microsoft said the bug is easy to exploit with repeatable success and released fixes in late May after the CVE was initially omitted from its May 2026 security updates. The vulnerability affects **SharePoint Server Subscription Edition**, **SharePoint Server 2019**, **SharePoint Server 2016**, and **SharePoint Enterprise Server 2016**. CISA ordered Federal Civilian Executive Branch agencies to remediate the issue within days under **BOD 26-04**, while internet scanning data cited by Shadowserver shows more than **10,000** SharePoint servers remain exposed online. Separately, Microsoft disclosed a ransomware investigation involving **Storm-2603** and another threat actor operating in the same compromised environment, where the attackers used persistence, remote access tools, privilege escalation, and defense evasion after initial access was likely obtained through **`CVE-2025-11371`** in Gladinet Triofox.
Jul 12, 2026
A critical Microsoft SharePoint remote code execution flaw, **CVE-2026-50522** (`CVSS 9.8`), is being actively exploited against on-premises deployments after Microsoft released fixes for affected versions of **SharePoint Enterprise Server 2016**, **SharePoint Server 2019**, and **SharePoint Subscription Edition**. The vulnerability stems from unsafe deserialization of untrusted data and can be triggered through unauthenticated requests, making internet-facing SharePoint farms particularly exposed. Researchers reported likely real-world exploitation against honeypots, and public proof-of-concept code is now available. Reporting indicates attackers have targeted on-prem SharePoint instances and, in some cases, stolen machine keys to help preserve long-term access. The flaw was originally demonstrated during **Pwn2Own Berlin**, where exploit code was shown and shared with Microsoft before the vendor issued patches. Organizations running exposed SharePoint servers have been urged to apply the fixed versions immediately and, if patching cannot be completed at once, restrict external access and review logs for suspicious requests to SharePoint sign-in pages.
Jul 22, 2026