Fresh SharePoint Vulnerability Exploited Soon After Disclosure
Threat actors have begun exploiting a fresh critical-severity remote code execution (RCE) vulnerability in Microsoft SharePoint, the US cybersecurity agency CISA warns.
Tracked as CVE-2026-58644 (CVSS score of 9.8) and fixed as part of Microsoft’s July 2026 Patch Tuesday updates, the flaw is described as a deserialization of untrusted data issue.
“In a network-based attack, an attacker authenticated as at least a Site Owner could write arbitrary code to inject and execute code remotely on the SharePoint Server,” Microsoft explains.
Microsoft’s security updates resolved several other SharePoint defects, including CVE-2026-56164, which was flagged as exploited in the wild as a zero-day, and CVE-2026-55040, a critical security bypass weakness that could allow attackers to disclose files and modify data.
Although CVE-2026-58644 was not initially marked as exploited, Microsoft has since updated its advisory to note that exploitation was detected and to update the vulnerability’s CVSS score.
On Thursday, two days after ...
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