Microsoft confirmed active attacks targeting on-premises SharePoint servers through a critical zero-day vulnerability. CNBC reports that the flaw allows hackers to gain complete system access and execute malicious code remotely. The vulnerability affects only self-hosted SharePoint installations, not cloud-based Microsoft 365 services.

Security researchers first detected the attacks on July 18, according to The Hacker News. The exploit, dubbed "ToolShell," targets CVE-2025-53770, rated with a maximum severity score of 9.8. Microsoft released emergency patches for two SharePoint versions while a third remains unprotected.

The U.S. Cybersecurity and Infrastructure Security Agency added the vulnerability to its Known Exploited Vulnerabilities catalog. CISA Acting Executive Assistant Director Chris Butera confirmed federal agencies must apply fixes by July 21. Eye Security, the Dutch firm that discovered the attacks, identified at least 54 compromised organizations across government, banking, and education sectors.

Government Systems and Critical Infrastructure at Risk

The SharePoint attacks have breached U.S. federal and state agencies, universities, and energy companies. The Washington Post reports that government officials in multiple states are scrambling to assess their exposure. One security expert described seeing "a mad scramble across the nation right now" as agencies work to protect their systems.

The vulnerability poses particular risks because SharePoint servers often connect to core Microsoft services like Outlook and Teams. This connectivity allows attackers to steal passwords, harvest data, and move laterally across networks. Researchers warn that compromised systems can maintain persistent access even after patches are applied through stolen cryptographic keys.

Nairametrics estimates over 10,000 organizations globally face exposure from internet-accessible SharePoint servers. The highest concentrations of vulnerable systems exist in the United States, Netherlands, United Kingdom, and Canada. Cybersecurity firm Censys warned this represents "a dream for ransomware operators" who are expected to target this vulnerability throughout the weekend.

Enterprise Security Landscape Faces New Challenges

The SharePoint breach represents another setback for Microsoft's cybersecurity reputation. The company has faced increasing scrutiny following previous incidents, including Chinese state-backed attacks on cloud systems and Exchange server compromises. The Washington Post notes that a U.S. government panel previously described Microsoft's security culture as "inadequate" after hackers accessed email systems of 22 organizations.

Microsoft's security business generates over $20 billion annually as enterprises consolidate vendors to reduce complexity. However, this market position means that vulnerabilities in Microsoft products can affect thousands of organizations simultaneously. The company has invested heavily in its Secure Future Initiative following criticism about patch quality and development practices.

The SharePoint attacks follow a pattern of threat actors quickly weaponizing vulnerabilities after security researchers publish technical details. The current exploit builds on a "ToolShell" attack demonstrated at the Pwn2Own competition in May 2025. Security experts emphasize that organizations must assume compromise and conduct thorough investigations even after applying patches, as attackers may have established persistent access through stolen system keys.

Further Reading

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