Microsoft SharePoint Zero-Day Vulnerability: What’s Happening Right Now
A critical Microsoft SharePoint zero-day vulnerability is under active attack, prompting urgent alerts from cybersecurity agencies and experts. This newly discovered flaw, identified as CVE-2025-53770, affects multiple versions of SharePoint Server—especially those self-hosted by organizations. With no immediate patches available for all affected systems, businesses are scrambling to defend themselves as hackers exploit the bug to steal private digital keys and deploy malware. The situation has already impacted U.S. federal agencies, energy companies, and universities, making it a widespread and high-stakes cyberthreat. If your organization uses on-premise SharePoint, understanding the threat and your response options is crucial.
Image Credits:Nicolas Economou / NurPhot / Getty Images
How the Microsoft SharePoint Zero-Day Vulnerability Works
The vulnerability is particularly dangerous because it allows attackers to bypass login credentials entirely. Once inside, hackers can extract digital keys from the SharePoint server. These keys enable them to impersonate legitimate users and access sensitive files, inject malware, and potentially spread to connected apps like Outlook, Teams, and OneDrive. The exploit doesn't require user interaction and affects even older versions such as SharePoint Server 2016.
What makes this exploit a "zero-day" is that Microsoft had no advance notice to fix it before it was discovered in the wild. According to Eye Security, which first publicized the flaw, dozens of compromised SharePoint servers were already detected online. This signals that the attackers had likely discovered and leveraged the vulnerability well before any public warning was issued.
Who Is Affected and Why It Matters Now
The scale of the attack is still unfolding, but the targets already include several U.S. federal agencies, universities, and private-sector entities. Small to mid-sized businesses are especially vulnerable, as they often lack the advanced security infrastructure needed to detect or block these attacks in real time.
The urgency of the situation is underscored by statements from cybersecurity experts like Michael Sikorski of Palo Alto Networks, who advised that if your on-premise SharePoint server is exposed to the internet, “you should assume that you have been compromised.” Organizations need to not only patch the bug (once a fix is available) but also rotate compromised digital keys and thoroughly audit their systems for further signs of intrusion.
What You Should Do About the Microsoft SharePoint Zero-Day Vulnerability
If your organization is running SharePoint Server on its own infrastructure, the first and most immediate step is to disconnect that system from the internet if possible. While Microsoft is still developing patches, cybersecurity agency CISA recommends taking "immediate recommended action" to mitigate risks. That includes isolating affected systems, rotating digital signing keys, and closely monitoring related applications for signs of tampering.
Given that the vulnerability compromises authentication mechanisms, even patched systems may remain at risk if digital keys are not updated. Organizations should also revisit their broader cybersecurity posture, considering past high-profile attacks against Microsoft platforms—including the Hafnium incident in 2021 and a Chinese cloud system breach in 2023.
To stay protected, IT teams must keep abreast of updates from Microsoft, apply any new security patches promptly, and review internal logs for any signs of suspicious access or data exfiltration. As this is an evolving threat, proactive defense is not just advisable—it’s necessary.
This Microsoft SharePoint zero-day vulnerability highlights the growing risks of relying on self-managed software infrastructure without robust, real-time security monitoring. As SharePoint connects with key productivity tools across the Microsoft ecosystem, the potential for widespread damage is high. Companies must take immediate precautions, even before official patches are available, to prevent further compromises. In today’s cybersecurity landscape, zero-day threats like CVE-2025-53770 are becoming more frequent—and far more damaging. Staying informed, prepared, and responsive is the only way forward.
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