CVE-2026-55040
Microsoft SharePoint Enterprise Server 2016, Microsoft SharePoint Server 2019, Microsoft SharePoint Server Subscription Edition
Published 14 Jul 2026 · updated 19 Aug 2026 · Analyzed
Exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on 18 Aug 2026, with a remediation deadline of 21 Aug 2026 for US federal agencies.
Required action: 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.
Description
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
References
- msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040 · Patch, Vendor Advisory
- github.com/sfewer-r7/CVE-2026-55040 · Exploit
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040 · Exploit, Third Party Advisory
- www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/ · US Government Resource