A critical SharePoint vulnerability, CVE-2026-55040, is being actively exploited by attackers after a public proof-of-concept was released on August 12, allowing unauthenticated users to impersonate administrators with a CVSS score of 9.1. The flaw, which was patched by Microsoft in July, enables attackers to bypass authentication and assume the identity of any SharePoint user or administrator without valid credentials. Exploitation began just days after the public proof-of-concept was made available, highlighting the importance of prompt patching. The vulnerability is considered critical, with a high CVSS score, and its exploitation status is being closely monitored by Microsoft. This vulnerability matters to practitioners because it poses a significant risk to unpatched SharePoint systems, making it essential to apply the July patch update to prevent potential attacks1.
SharePoint CVE-2026-55040 Comes Under Attack Following Public Exploit
⚠️ Critical Alert
Why This Matters
CVE-2026-55040 is in active discussion involving Microsoft — exploitation status determines whether this is patch-now or monitor.
References
- SecurityAffairs. (2026, August 13). SharePoint CVE-2026-55040 Comes Under Attack Following Public Exploit. *SecurityAffairs*. https://securityaffairs.com/197137/hacking/sharepoint-cve-2026-55040-comes-under-attack-following-public-exploit.html
Original Source
SecurityAffairs
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