{"id":"CVE-2021-26855","aliases":[],"url":"https://o3.security/vulnerability/CVE-2021-26855","summary":"Microsoft Exchange Server Remote Code Execution Vulnerability","details":"Microsoft Exchange Server Remote Code Execution Vulnerability","published":"2021-03-03T00:15:12.103","modified":"2026-08-19T19:22:24.100","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":{"score":0.99996,"percentile":0.99989,"asOf":"2026-09-17"},"cisaKev":{"dateAdded":"2021-11-03","dueDate":"2022-05-03","knownRansomwareCampaignUse":true},"exploitsKnown":90,"affectedPackages":[],"fix":null,"references":[{"type":"FIX","url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26855"},{"type":"EXPLOIT","url":"http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html"},{"type":"EXPLOIT","url":"http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html"},{"type":"EXPLOIT","url":"http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html"},{"type":"EXPLOIT","url":"http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html"},{"type":"FIX","url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855"},{"type":"WEB","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26855"}],"provenance":{"sources":["OSV.dev","NVD","CISA KEV","FIRST.org (EPSS)"],"lastVerified":"2026-08-19T19:22:24.100"}}