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SharePoint CVE-2026-55040 Comes Under Attack Following Public Exploit
Attackers are actively exploiting critical SharePoint authentication bypass CVE-2026-55040 (CVSS 9.1) days after Rapid7 released a public PoC.
CVE-2026-55040 is a critical authentication bypass (CVSS 9.1) in SharePoint Server Subscription Edition that lets unauthenticated attackers forge JWT tokens and impersonate any user, including administrators. Microsoft patched it in July 2026 Patch Tuesday, but Rapid7 published a technical write-up and Python PoC on GitHub on August 12, and Defused quickly observed attackers running the PoC against SharePoint honeypots. KEVIntel recorded 12 exploitation attempts since July 19, with eight occurring on August 12-13 from IP addresses in Hong Kong, Japan, the Netherlands, Taiwan and the U.S. Admin-level SharePoint access exposes documents and data modification and can serve as a foothold into broader Microsoft 365 infrastructure; unpatched instances should apply the July update immediately.
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Unpatched Zimbra servers are falling to CVE-2026-73570 attacks
Attackers are exploiting unpatched Zimbra servers via CVE-2026-73570; 274 instances compromised, and CISA added the flaw to its KEV catalog.
The Shadowserver Foundation counted at least 274 compromised internet-facing Zimbra Collaboration Suite instances exploited through CVE-2026-73570, up from 155 on August 20. The unauthenticated code injection flaw affects servers with the optional zimbra-snmp package and SNMP notifications enabled, allowing arbitrary OS command execution via crafted SMTP requests. Synacor patched the issue in ZCS v10.1.20 on July 20, 2026, and at least 8,200 instances remain unpatched. CISA added the flaw to its Known Exploited Vulnerabilities catalog and gave US federal civilian agencies three days to remediate and check for compromise.
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