Understanding the SharePoint Zero-Day Vulnerability
A critical SharePoint zero-day vulnerability—identified as CVE-2025-53770—is currently being actively exploited by China-backed hackers, according to Google and Microsoft. This vulnerability affects self-hosted SharePoint servers and allows attackers to steal sensitive private keys, install malware, and access internal company documents and network systems. Because this is a zero-day exploit, Microsoft had no opportunity to release a patch before it began being used in attacks. The flaw was discovered in mid-July 2025, and cybercriminals have since breached dozens of organizations, including those in the government sector.
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The hackers are targeting organizations that rely on self-managed SharePoint installations, which are widely used to store and manage confidential files. This makes the vulnerability extremely dangerous for companies that have not applied Microsoft’s recent security patches. Microsoft’s cybersecurity division has now attributed these attacks to three Chinese threat groups—Linen Typhoon, Violet Typhoon, and Storm-2603—all of which have a history of espionage, data theft, and even ransomware deployment.
Who’s Behind the SharePoint Zero-Day Attacks?
Microsoft’s investigation points to three distinct hacker groups operating with support from the Chinese state. Linen Typhoon is believed to focus primarily on stealing intellectual property, often from tech and research organizations. Violet Typhoon, on the other hand, specializes in collecting personal and strategic information for espionage. The third group, Storm-2603, remains lesser-known, though Microsoft believes it may have ties to earlier ransomware campaigns.
Google’s Mandiant unit also confirmed these details, noting that “multiple actors are now actively exploiting this vulnerability.” According to Google, at least one of the groups has a strong China nexus, though the attacks are no longer isolated to one actor. The vulnerability has already allowed malicious access to key systems across multiple industries, and the full scope of the damage is still being assessed.
Why the SharePoint Zero-Day Matters Globally
Zero-day vulnerabilities like CVE-2025-53770 are especially dangerous because they give hackers a head start before the public or vendors can react. The fact that this bug targets SharePoint—a widely used enterprise collaboration platform—escalates the risk. Cybersecurity researchers warn that companies using self-hosted versions of SharePoint should immediately apply Microsoft’s newly released patches and also assume they may already be compromised.
This incident mirrors previous China-linked cyberattacks, including the 2021 “Hafnium” attack on Microsoft Exchange servers, which affected over 60,000 systems worldwide. Despite China’s repeated denials of involvement, global security experts consistently link advanced persistent threats (APTs) like these to nation-state operations. While the Chinese government publicly states that it “firmly opposes all forms of cyber crime,” evidence continues to mount pointing to coordinated state-sponsored cyber espionage.
How to Protect Against the SharePoint Zero-Day Vulnerability
Organizations using SharePoint must take immediate action to defend against this threat. First, apply Microsoft’s security patches for all affected versions of SharePoint without delay. Next, conduct a full forensic audit to determine whether systems have already been breached. Network administrators should monitor for signs of malware or suspicious file access, particularly on self-hosted servers.
It’s also critical to implement strong access controls, segment sensitive systems, and use endpoint detection tools to spot any lingering threats. For businesses that cannot ensure full patching or real-time threat monitoring, migrating from self-hosted SharePoint to a cloud-based or managed platform may offer better protection. In the long run, cyber resilience depends on a combination of proactive patch management, real-time threat detection, and an incident response plan that assumes breach as a possibility.
The SharePoint zero-day vulnerability being exploited by China-linked hackers highlights the evolving threat landscape facing enterprises in 2025. As attackers grow more sophisticated and vulnerabilities become more severe, companies must prioritize cybersecurity hygiene and adopt a zero-trust mindset. Microsoft and Google’s findings serve as a wake-up call: no organization is immune, and rapid response is key to minimizing damage from these stealthy and highly targeted campaigns.
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