A major security vulnerability in Microsoft's widely used Sharepoint server software has been exploited by hackers, causing chaos within businesses and government agencies.

The incident has reportedly impacted the servers of federal agencies, schools, and energy companies. Some emergency patches have been deployed. On July 19, Microsoft alerted users that it was experiencing an active cyberattack on its SharePoint servers,

Microsoft has released security patches for the zero-day vulnerability chain dubbed ToolShell, capable of remote code execution on SharePoint, resulting in the exploitation of at least 54 organizations worldwide.

Multiple hacking groups—including state actors from China—have targeted a vulnerability in older, on-premises versions of the file-sharing tool after a flawed attempt to patch it.

The zero-day vulnerability — which was first disclosed late Saturday — has been exploited by several Chinese state-aligned groups, according to Microsoft.

Microsoft is issuing an emergency fix to close off a vulnerability in Microsoft’s SharePoint software that hackers have exploited to carry out widespread attacks on businesses and at least some federal agencies.

CISA gave agencies until the end of the day on Monday to mitigate a severe zero-day vulnerability in Microsoft's widely used SharePoint software.