{"id":"CVE-2026-56191","aliases":["EUVD-2026-48458","GHSA-w7qh-jvr9-qmx9"],"status":"published","title":"Microsoft Exchange Online Tampering Vulnerability","description":"Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.","severity":{"version":"3.1","score":10,"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","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00901,"percentile":0.59952,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-287"],"published":"2026-07-24T00:01:12Z","modified":"2026-11-01T17:37:54Z","products":[{"vendor":"","product":"microsoft exchange online"},{"vendor":"microsoft","product":"exchange_online"},{"vendor":"microsoft","product":"microsoft exchange online"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191","tags":["vendor-advisory","patch","Vendor Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56191"},{"url":"https://github.com/advisories/GHSA-w7qh-jvr9-qmx9"}],"sources":{"cve":[{"id":"CVE-2026-56191","title":"Microsoft Exchange Online Tampering Vulnerability","description":"Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.","status":"published","published":"2026-07-24T00:01:12.361Z","modified":"2026-11-01T17:37:54.584Z","cvss":[{"version":"3.1","score":10,"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","level":"critical","assessor":"cna"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T13:36:51.6229Z"}],"euvd":[{"id":"EUVD-2026-48458","description":"Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.","status":"published","published":"2026-07-24T00:01:12Z","modified":"2026-11-01T17:37:54Z","cvss":[{"version":"3.1","score":10,"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","level":"critical"}],"updated_at":"2026-11-02T16:58:46.574424Z"}],"ghsa":[{"id":"GHSA-w7qh-jvr9-qmx9","title":"Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform...","description":"Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.","status":"published","published":"2026-07-24T03:31:55Z","modified":"2026-07-24T03:32:01Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T15:09:45.375488Z"}],"nvd":[{"id":"CVE-2026-56191","description":"Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.","status":"published","published":"2026-07-24T01:17:36.417Z","modified":"2026-10-24T13:10:00.147Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"secondary"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T14:12:32.473901Z"}]}}