{"id":"CVE-2021-34523","aliases":["EUVD-2021-21177","GHSA-gcrr-725q-f8jw"],"status":"published","title":"Microsoft Exchange Server Elevation of Privilege Vulnerability","description":"Microsoft Exchange Server Elevation of Privilege Vulnerability","severity":{"version":"3.1","score":9,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N/E:U/RL:O/RC:C","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.9999,"percentile":0.99985,"model":"v2026.06.15"},"facts":{"in_kev":true,"known_exploited":true,"public_exploit":true,"fix_available":false},"cwes":["CWE-269","CWE-287"],"published":"2021-07-14T17:54:38Z","modified":"2026-08-10T19:59:11Z","kev":{"date_added":"2021-11-03","due_date":"2021-11-17","required_action":"Apply updates per vendor instructions.","known_ransomware_use":"Known"},"exploitation":[{"source":"euvd","since":"2021-11-03"},{"source":"kev","since":"2021-11-03"}],"exploits":[{"source":"metasploit","id":"exploit/windows/http/exchange_proxyshell_rce","title":"Microsoft Exchange ProxyShell RCE","type":"exploit","platform":"Windows","date":"2021-04-06","verified":true,"url":"https://www.rapid7.com/db/modules/exploit/windows/http/exchange_proxyshell_rce"},{"source":"pocgithub","id":"mithridates1313/ProxyShell_POC","title":"mithridates1313/ProxyShell_POC","date":"2021-10-02","url":"https://github.com/mithridates1313/ProxyShell_POC"},{"source":"pocgithub","id":"SUPRAAA-1337/CVE-2021-34523","title":"SUPRAAA-1337/CVE-2021-34523","date":"2023-09-02","url":"https://github.com/SUPRAAA-1337/CVE-2021-34523"}],"products":[{"vendor":"microsoft","product":"exchange server"},{"vendor":"microsoft","product":"exchange_server"},{"vendor":"microsoft","product":"microsoft exchange server 2013 cumulative update 23"},{"vendor":"microsoft","product":"microsoft exchange server 2016 cumulative update 19"},{"vendor":"microsoft","product":"microsoft exchange server 2016 cumulative update 20"},{"vendor":"microsoft","product":"microsoft exchange server 2019 cumulative update 8"},{"vendor":"microsoft","product":"microsoft exchange server 2019 cumulative update 9"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523","tags":["vendor-advisory","patch","Patch","Vendor Advisory"]},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523","tags":["x_refsource_MISC","x_transferred","Patch","Vendor Advisory"]},{"url":"https://www.zerodayinitiative.com/advisories/ZDI-21-822/","tags":["x_refsource_MISC","x_transferred","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html","tags":["x_refsource_MISC","x_transferred","Exploit","Third Party Advisory","VDB Entry"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523","tags":["government-resource","US Government Resource"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-34523"},{"url":"https://www.zerodayinitiative.com/advisories/ZDI-21-822"},{"url":"https://github.com/advisories/GHSA-gcrr-725q-f8jw"}],"sources":{"cve":[{"id":"CVE-2021-34523","title":"Microsoft Exchange Server Elevation of Privilege Vulnerability","description":"Microsoft Exchange Server Elevation of Privilege Vulnerability","status":"published","published":"2021-07-14T17:54:38Z","modified":"2026-08-10T15:11:21.458Z","cvss":[{"version":"3.1","score":9,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N/E:U/RL:O/RC:C","level":"critical","assessor":"cna"}],"updated_at":"2026-11-02T14:33:11.59359Z"}],"euvd":[{"id":"EUVD-2021-21177","description":"Microsoft Exchange Server Elevation of Privilege 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Server contains an unspecified vulnerability that allows for privilege escalation.","cwes":["CWE-287"],"kev":{"date_added":"2021-11-03","due_date":"2021-11-17","required_action":"Apply updates per vendor instructions.","known_ransomware_use":"Known"},"updated_at":"2026-11-02T17:00:17.050017Z"}],"nvd":[{"id":"CVE-2021-34523","description":"Microsoft Exchange Server Elevation of Privilege Vulnerability","status":"published","published":"2021-07-14T18:15:12.347Z","modified":"2026-08-10T19:59:11.883Z","cvss":[{"version":"3.1","score":9,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N","level":"critical","assessor":"secondary"},{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"secondary"},{"version":"2.0","score":7.5,"vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","level":"high","assessor":"primary"}],"updated_at":"2026-11-02T14:06:55.747384Z"}]}}