CVE-2026-56191: critical vulnerability in Microsoft Exchange Online
Microsoft Exchange Online Tampering Vulnerability
Published · Updated
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
28Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 10epss 0.9%
Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
Affected products
Microsoft · Microsoft Exchange OnlineRelated CVEs — Microsoft Exchange Online
In the same product, most dangerous first.
CVE-2026-48579CRITICALMicrosoft Exchange Online Information Disclosure VulnerabilityEPSS 1.0%CVE-2026-65801CRITICALMicrosoft Exchange Online Elevation of Privilege VulnerabilityEPSS 0.9%CVE-2026-54998HIGHMicrosoft Exchange Online Elevation of Privilege VulnerabilityEPSS 0.8%CVE-2026-48582CRITICALMicrosoft Exchange Online Elevation of Privilege VulnerabilityEPSS 0.7%CVE-2026-26137CRITICALMicrosoft Exchange Elevation of Privilege VulnerabilityEPSS 0.6%CVE-2026-96185HIGHMicrosoft Exchange Online Remote Code Execution VulnerabilityEPSS 0.5%