CISA has added CVE‑2026-56164, named Microsoft SharePoint Server Missing Authentication for Critical Function Vulnerability, to its Known Exploited Vulnerabilities catalogue. The affected vendor is Microsoft and the product is SharePoint Server. The vulnerability allows an unauthenticated attacker to elevate privileges over a network by exploiting a missing authentication check on a critical function.
The flaw is a missing authentication bypass that can be triggered remotely, leading to privilege escalation on the affected SharePoint Server. It has a CVSS v3.1 base score of 5.3, rated MEDIUM, and the attack vector is network‑based. Microsoft has released a patch; the advisory and update guidance are available via the MSRC link provided in the notes.
Active exploitation of this vulnerability has been confirmed, which is the basis for its inclusion in the KEV catalogue. No known ransomware campaign use has been reported at this time. CISA has set a remediation deadline of 17 July 2026 for federal agencies to apply the required mitigations.
CISA’s required action is: “Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable.
Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.” This directive binds Federal Civilian Executive Branch (FCEB) agencies; all other organisations should review their SharePoint Server exposure and apply the patch or mitigations as soon as practicable.
For full details, consult the NVD entry at https://nvd.nist.gov/vuln/detail/CVE-2026-56164 and the CISA KEV catalogue.