CVE-2026-55040: Microsoft SharePoint JWT Token Authentication Bypass (FIXED)

Sicherheitsmeldung mit Schweregrad noch nicht bewertet. Betroffene Kennungen: CVE-2026-55040. Technische Details im Tab „Originaltext“; empfohlene Schritte in der Checkliste.

Originaltext der Quelle (nicht übersetzt) – die deutsche Zusammenfassung findest du im Tab „Kurzfassung".

OverviewRapid7 Labs conducted a zero-day research project against Microsoft SharePoint, resulting in the discovery of two new vulnerabilities that, when chained together, achieve unauthenticated remote code execution (RCE) against a vulnerable SharePoint server. Today, both Rapid7 and Microsoft are disclosing the first vulnerability in this chain, the authentication bypass vulnerability CVE-2026-55040. The RCE component of the exploit chain is expected to be patched by Microsoft in the next update cycle for August 2026. The exploit chain was developed as an entry for the recent Pwn2Own Berlin hacking competition – part of Rapid7 Labs' continued effort to raise the bar in Vulnerability Intelligence and our commitment to the preemptive protection of our customers through original vulnerability research.A remote unauthenticated attacker can leverage CVE-2026-55040 to bypass authentication on a vulnerable SharePoint server and perform operations as a SharePoint site user or administrator. The vulnerability is due to several issues in the JWT token validation pipeline.CVE-2026-55040 has a CVSSv3.1 score of 5.3 (Medium), and a Common Weakness Enumeration (CWE) of CWE-1390: Weak Authentication.Product descriptionMicrosoft SharePoint is a ubiquitous, web-based collaboration and document management platform deeply integrated into the Microsoft 365 ecosystem. Serving as the central hub for corporate intranets, internal file sharing, and workflow automation, it is trusted by enterprises worldwide to store and manage vast repositories of sensitive business data. Because SharePoint …

Vollständiger Originalartikel ↗

• Betroffenheit im eigenen Stack prüfen (CVE-2026-55040): Versionen/Komponenten abgleichen.
• Originalquelle / Hersteller-Advisory lesen: https://www.rapid7.com/blog/post/ve-cve-2026-55040-microsoft-sharepoint-jwt-token-authentication-bypass-fixed
• Verfügbaren Patch oder Workaround einspielen und dokumentieren.