CISA has issued a warning about multiple actively exploited vulnerabilities in Microsoft SharePoint Server. These include CVE-2026-45659, CVE-2026-50522, and CVE-2026-58644, all involving the deserialization of untrusted data. Exploitation allows attackers to run arbitrary code remotely, posing significant security risks to affected systems.
CVE-2026-45659 allows an authenticated attacker with site member permissions to execute arbitrary code on impacted SharePoint servers. Initially assessed as 'Exploitation Less Likely' by Microsoft, it was marked by CISA due to increased exploitation.
In addition, CVE-2026-50522, with a CVSS score of 9.8, emerged following the release of proof-of-concept exploit code targeting SharePoint's deserialization flaw, leading to unauthorized access and potential data compromise.
Microsoft issued patches in its July 2026 security updates to address these vulnerabilities. These updates aim to reduce exploitation risks by correcting the underlying flaws across multiple SharePoint versions, including Subscription Edition and Server 2019.
CISA has mandated federal agencies patch these vulnerabilities under its Known Exploited Vulnerabilities (KEV) guidelines by specific deadlines. Prompt patching is crucial to mitigate potential damage from these security breaches.
Organizations using Microsoft SharePoint are advised to implement the provided patches immediately. Failure to do so may result in unauthorized access and persistent threats, notably from attackers leveraging these exploits to breach critical systems.
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