{"id":"CVE-2026-55009","title":"Microsoft Exchange Server Elevation of Privilege Vulnerability","summary":"Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C","cvssSource":"cna","cwe":["CWE-502"],"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 23","affected":["exchange_server_2016_cumulative_update_23 >= 15.01.0.0 < 15.01.2507.071","exchange_server_2019_cumulative_update_14 >= 15.02.0.0 < 15.02.1544.043","exchange_server_2019_cumulative_update_15 >= 15.02.0.0 < 15.02.1748.048","exchange_server_subscription_edition_rtm >= 15.02.0.0 < 15.02.2562.045"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-07-13T00:00:00+00:00"},"published":"2026-07-14","updated":"2026-09-17","sourceUpdated":"2026-09-17T22:29:03.227Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-55009","references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55009","label":"Microsoft Exchange Server Elevation of Privilege Vulnerability"}],"tags":["cve.org"],"epss":0.02513,"epssPercentile":0.83993,"ingestedAt":"2026-09-08T17:06:31.929Z","slug":"CVE-2026-55009","body":"## Overview\n\nDeserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.\n\n## Affected\n\n- `exchange_server_2016_cumulative_update_23 >= 15.01.0.0 < 15.01.2507.071`\n- `exchange_server_2019_cumulative_update_14 >= 15.02.0.0 < 15.02.1544.043`\n- `exchange_server_2019_cumulative_update_15 >= 15.02.0.0 < 15.02.1748.048`\n- `exchange_server_subscription_edition_rtm >= 15.02.0.0 < 15.02.2562.045`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0.5,"exploitation":0,"ransomware":0},"changes":[]}