CVE-2026-55040
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
Actively exploited
- In the CISA exploited-vulnerabilities catalogue since Aug 18, 2026
- US federal agencies must remediate it by Aug 21, 2026 (BOD 22-01)
- First attack observed 28 days after disclosure
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.
Source: CISA KEV · Sep 8, 2026 Aug 25, 2026 Aug 18, 2026 Aug 14, 2026 Aug 12, 2026 Aug 12, 2026
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NAffected products
| Vendors | Product | Versions |
|---|---|---|
| microsoft | sharepoint server | < 16.0.19725.20434 |
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