{"schema":"threatline.record/2","record":{"id":"CVE-2021-34473","aliases":[],"summary":"Microsoft Exchange Server Remote Code Execution Vulnerability","details":"Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution.","categories":["Applications & CMS"],"product":"Exchange Server","vendor":"Microsoft","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Exchange Server 2013 Cumulative Update 23","vendor":"Microsoft","versions":[{"version":"15.00.0","lessThan":"15.00.1497.015","versionType":"custom","status":"affected"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Exchange Server 2016 Cumulative Update 19","vendor":"Microsoft","versions":[{"version":"15.01.0","lessThan":"15.01.2176.012","versionType":"custom","status":"affected"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Exchange Server 2016 Cumulative Update 20","vendor":"Microsoft","versions":[{"version":"15.01.0","lessThan":"15.01.2242.008","versionType":"custom","status":"affected"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Exchange Server 2019 Cumulative Update 8","vendor":"Microsoft","versions":[{"version":"15.02.0","lessThan":"15.02.0792.013","versionType":"custom","status":"affected"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Exchange Server 2019 Cumulative Update 9","vendor":"Microsoft","versions":[{"version":"15.02.0","lessThan":"15.02.0858.010","versionType":"custom","status":"affected"}],"defaultStatus":null}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft Exchange Server 2013 Cumulative Update 23","ecosystem":null},"version":"15.00.1497.015","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft Exchange Server 2016 Cumulative Update 19","ecosystem":null},"version":"15.01.2176.012","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft Exchange Server 2016 Cumulative Update 20","ecosystem":null},"version":"15.01.2242.008","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft Exchange Server 2019 Cumulative Update 8","ecosystem":null},"version":"15.02.0792.013","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","source_modified_at":"2026-08-10T15:11:21.909Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft Exchange Server 2019 Cumulative Update 9","ecosystem":null},"version":"15.02.0858.010","basis":"first unaffected version stated in the CVE record"}],"cvss":9.1,"severity":"Critical","kev":{"listed":true,"date_added":"2021-11-03","due_date":"2021-11-17","required_action":"Apply updates per vendor instructions.","ransomware_campaign_use":"Known"},"epss":{"probability":0.99999,"percentile":0.99997,"score_date":"2026-10-23"},"published_at":"2021-07-14T17:54:03.000Z","modified_at":"2026-08-10T15:11:21.909Z","provenance":[{"source":"CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23T17:00:09.9001Z"},{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2021-34473","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-08-10T15:11:21.909Z"},{"source":"Metasploit","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/http/exchange_proxyshell_rce.rb","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2021-04-06"},{"source":"Nuclei","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-34473.yaml","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":null},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-34473","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CISA KEV","CVE List","Metasploit","Nuclei","EPSS"],"references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-34473","source":"CISA KEV"},{"source":"CVE List","url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34473","tags":["vendor-advisory","patch"]},{"source":"CVE List","url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34473","tags":["x_refsource_MISC","x_transferred"]},{"source":"CVE List","url":"https://www.zerodayinitiative.com/advisories/ZDI-21-821/","tags":["x_refsource_MISC","x_transferred"]},{"source":"CVE List","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34473","tags":["government-resource"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"active","automatable":"yes","technical_impact":"total","assessed_at":"2025-02-04T15:42:23.926450Z"},"exploits":[{"source":"Metasploit","kind":"Exploit module","name":"Microsoft Exchange ProxyShell RCE","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/http/exchange_proxyshell_rce.rb","date":"2021-04-06","added":"2026-04-22","check":true},{"source":"Nuclei","kind":"Scanner template","name":"Exchange Server - Remote Code Execution","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-34473.yaml"}],"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-08-10T15:11:21.909Z","content_hash":"bc5e05b040773178b9f7d36274181d69aa8496f5fafb9d587f65ff2635b260ff"}}