{"affected":[{"product":"Microsoft Exchange Online","source":"CNA: microsoft","vendor":"Microsoft","versions":[{"status":"affected","version":"-"}]}],"cveId":"CVE-2026-56191","cwes":["CWE-287"],"description":"Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.","epss":{"date":"2026-11-10","percentile":0.6,"score":0.00901},"exploits":[],"kev":null,"metrics":[{"score":10,"severity":"critical","source":"CNA: microsoft","vector":"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","version":"3.1"}],"modifiedAt":1794350468340,"publishedAt":1784851272361,"references":[{"source":"CNA: microsoft","tags":["vendor-advisory","patch"],"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191"}],"remediation":[{"kind":"fix","source":"CNA: microsoft","text":"The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.","url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191"}],"revision":"c16fd6877cdc9abe468abe2964c29464802f4d26b3f28c3c586d18138aa46de7","sources":[{"modifiedAt":1794350468340,"name":"CNA: microsoft","retrievedAt":1794353168496,"url":"https://www.cve.org/CVERecord?id=CVE-2026-56191"},{"modifiedAt":null,"name":"FIRST EPSS","retrievedAt":1794353191713,"url":"https://api.first.org/data/v1/epss?cve=CVE-2026-56191"}],"ssvc":{"assessedAt":1784851200000,"automatable":"yes","exploitation":"none","source":"ADP: CISA-ADP","technicalImpact":"total"},"status":"published","title":"Microsoft Exchange Online Tampering Vulnerability","updatedAt":1794353191713}