{"id":"CVE-2021-42321","title":"Microsoft Exchange Server Remote Code Execution Vulnerability","summary":"Microsoft Exchange Server Remote Code Execution Vulnerability","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","vendor":"microsoft","product":"exchange_server","affected":["exchange_server = 2016","exchange_server = 2019"],"published":"2021-11-10","updated":"2026-08-19","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2021-42321","references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42321","label":"secure@microsoft.com"},{"url":"http://packetstormsecurity.com/files/166153/Microsoft-Exchange-Server-Remote-Code-Execution.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://packetstormsecurity.com/files/168131/Microsoft-Exchange-Server-ChainedSerializationBinder-Remote-Code-Execution.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42321","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42321","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd","kev","in-the-wild","exploit-available"],"epss":0.91737,"epssPercentile":0.99813,"kev":true,"kevDateAdded":"2021-11-17","kevDueDate":"2021-12-01","kevRansomware":true,"exploited":true,"ingestedAt":"2026-08-20T17:59:03.379Z","exploits":{"github":3,"githubRepos":["https://github.com/DarkSprings/CVE-2021-42321","https://github.com/timb-machine-mirrors/testanull-CVE-2021-42321_poc.py","https://github.com/7BitsTeam/exch_CVE-2021-42321"],"metasploit":["exploit/windows/http/exchange_chainedserializationbinder_rce"],"checkedAt":"2026-09-25T08:20:39.888Z"},"exploitAvailable":true,"slug":"CVE-2021-42321","body":"## Overview\n\nMicrosoft Exchange Server Remote Code Execution Vulnerability\n\n## Affected\n\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":97,"depthScoreParts":{"impact":48.4,"likelihood":18.3,"exploitation":25,"ransomware":5},"changes":[{"seq":4550,"id":"CVE-2021-42321","ts":1788887189734,"field":"exploit_available","old":"false","new":"true"},{"seq":3433,"id":"CVE-2021-42321","ts":1788886306979,"field":"exploit_available","old":"true","new":"false"},{"seq":2288,"id":"CVE-2021-42321","ts":1788882976693,"field":"exploit_available","old":"false","new":"true"},{"seq":1317,"id":"CVE-2021-42321","ts":1788882388658,"field":"exploit_available","old":"true","new":"false"},{"seq":431,"id":"CVE-2021-42321","ts":1788881824249,"field":"exploit_available","old":"false","new":"true"}]}