{"id":"CVE-2021-26857","title":"Microsoft Exchange Server Remote Code Execution Vulnerability","summary":"Microsoft Exchange Server Remote Code Execution Vulnerability","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cwe":["CWE-502","CWE-502"],"vendor":"microsoft","product":"exchange_server","affected":["exchange_server = 2010","exchange_server = 2013","exchange_server = 2016","exchange_server = 2019"],"published":"2021-03-03","updated":"2026-08-12","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2021-26857","references":[{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857","label":"secure@microsoft.com"},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26857","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd","kev","in-the-wild","exploit-available"],"epss":0.95762,"epssPercentile":0.99872,"kev":true,"kevDateAdded":"2021-11-03","kevDueDate":"2022-05-03","kevRansomware":true,"exploited":true,"zeroDay":true,"ingestedAt":"2026-08-12T19:54:25.677Z","exploits":{"github":1,"githubRepos":["https://github.com/sirpedrotavares/Proxylogon-exploit"],"checkedAt":"2026-09-21T15:24:11.450Z"},"exploitAvailable":true,"slug":"CVE-2021-26857","body":"## Overview\n\nMicrosoft Exchange Server Remote Code Execution Vulnerability\n\n## Affected\n\n- `exchange_server = 2010`\n- `exchange_server = 2013`\n- `exchange_server = 2016`\n- `exchange_server = 2019`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"abyssal","depthScore":92,"depthScoreParts":{"impact":42.9,"likelihood":19.2,"exploitation":25,"ransomware":5},"changes":[{"seq":4512,"id":"CVE-2021-26857","ts":1788887186267,"field":"exploit_available","old":"false","new":"true"},{"seq":3395,"id":"CVE-2021-26857","ts":1788886303976,"field":"exploit_available","old":"true","new":"false"},{"seq":2250,"id":"CVE-2021-26857","ts":1788882973589,"field":"exploit_available","old":"false","new":"true"},{"seq":1279,"id":"CVE-2021-26857","ts":1788882385273,"field":"exploit_available","old":"true","new":"false"},{"seq":393,"id":"CVE-2021-26857","ts":1788881820620,"field":"exploit_available","old":"false","new":"true"}]}