{"id":"CVE-2021-34523","title":"Microsoft Exchange Server Elevation of Privilege Vulnerability","summary":"Microsoft Exchange Server Elevation of Privilege Vulnerability","severity":"critical","cvss":9,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N","vendor":"microsoft","product":"exchange_server","affected":["exchange_server = 2013","exchange_server = 2016","exchange_server = 2019"],"published":"2021-07-14","updated":"2026-08-10","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2021-34523","references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523","label":"secure@microsoft.com"},{"url":"http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.zerodayinitiative.com/advisories/ZDI-21-822/","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd","kev","in-the-wild","exploit-available"],"epss":0.9999,"epssPercentile":0.99985,"kev":true,"kevDateAdded":"2021-11-03","kevDueDate":"2021-11-17","kevRansomware":true,"exploited":true,"zeroDay":true,"ingestedAt":"2026-08-10T16:41:17.511Z","exploits":{"github":2,"githubRepos":["https://github.com/mithridates1313/ProxyShell_POC","https://github.com/SUPRAAA-1337/CVE-2021-34523"],"metasploit":["exploit/windows/http/exchange_proxyshell_rce"],"checkedAt":"2026-09-08T15:36:49.431Z"},"exploitAvailable":true,"slug":"CVE-2021-34523","body":"## Overview\n\nMicrosoft Exchange Server Elevation of Privilege Vulnerability\n\n## Affected\n\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":"hadal","depthScore":99,"depthScoreParts":{"impact":49.5,"likelihood":20,"exploitation":25,"ransomware":5},"changes":[{"seq":4526,"id":"CVE-2021-34523","ts":1788887187861,"field":"exploit_available","old":"false","new":"true"},{"seq":3409,"id":"CVE-2021-34523","ts":1788886305529,"field":"exploit_available","old":"true","new":"false"},{"seq":2264,"id":"CVE-2021-34523","ts":1788882975008,"field":"exploit_available","old":"false","new":"true"},{"seq":1293,"id":"CVE-2021-34523","ts":1788882386831,"field":"exploit_available","old":"true","new":"false"},{"seq":407,"id":"CVE-2021-34523","ts":1788881822620,"field":"exploit_available","old":"false","new":"true"}]}