{"id":"CVE-2021-31206","published":"2021-07-14T17:53:13Z","modified":"2026-08-10T15:11:29Z","title":"Microsoft Exchange Server Remote Code Execution Vulnerability","vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 23","tier":"core","eol":null,"affectedVersions":[{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 23","versions":[">= 15.00.0, < 15.00.1497.023"]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 20","versions":[">= 15.01.0, < 15.01.2242.012"]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 21","versions":[">= 15.01.0, < 15.01.2308.014"]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 10","versions":[">= 15.02.0, < 15.02.0922.013"]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 9","versions":[">= 15.02.0, < 15.02.0858.015"]}],"description":{"text":"Microsoft Exchange Server Remote Code Execution Vulnerability","provenance":"source","from":"CVE.org"},"summary":{"text":"Microsoft Exchange Server 2013 Cumulative Update 23 contains a remote code execution vulnerability in the Exchange Server component. An unauthenticated remote attacker over the network can exploit it with low complexity, but it requires a user to interact with the crafted content or request.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:15:38Z"},"cvss":{"score":7.6,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:L/E:F/RL:O/RC:C","provenance":"source","from":"CVE.org CNA"},"epss":{"score":0.13006,"percentile":0.96322,"date":"2026-10-29","provenance":"source"},"kev":null,"vulncheckKev":{"dateAdded":"2022-01-17","exploitedFirstSeen":"2022-01-17","ransomware":true,"evidence":[{"url":"https://blog.cyble.com/2022/01/17/avoslocker-ransomware-linux-version-targets-vmware-esxi-servers/","date":"2022-01-17"},{"url":"https://cybersecurityworks.com/howdymanage/uploads/file/RansomwareUpdate%20Report%202022%20Q1.pdf","date":"2022-04-12"},{"url":"https://cybersecurityworks.com/howdymanage/uploads/file/Spotlight%20Report%20-%20Index%20Update%20Q2%20-%20Q3%20-%20Final%20Version_compressed.pdf","date":"2022-05-18"},{"url":"https://static.tenable.com/marketing/whitepapers/Whitepaper-Ransomware_Ecosystem.pdf","date":"2022-06-22"},{"url":"https://cisa.gov/news-events/cybersecurity-advisories/aa22-257a","date":"2022-09-14"},{"url":"https://www.ivanti.com/resources/v/doc/pr-survey-report/ransomware-quarterly-indexreport_q2-q3","date":"2022-10-21"},{"url":"https://www.hhs.gov/sites/default/files/iranian-threat-actors-and-healthcare.pdf","date":"2022-11-03"},{"url":"https://info.securin.io/hubfs/Securin%20Ransomware%20Report%202023.pdf","date":"2023-02-14"}],"evidenceTotal":8,"provenance":"source"},"exploited":true,"otx":{"pulseCount":24,"pulses":[{"name":"APT29","url":"https://otx.alienvault.com/pulse/69f46a108000bd36fe90d5be","created":"2026-05-01"},{"name":"Spam “Broken Seal” DocuSign-themed Delivery w/Fileless Process Hollowing (Zeppelin/Bloat-A) by msudosos","url":"https://otx.alienvault.com/pulse/69bf64eccb5d39a90a3c391e","created":"2026-03-22"},{"name":"Spam “Broken Seal” DocuSign-themed Delivery w/Fileless Process Hollowing (Zeppelin/Bloat-A) by msudosos","url":"https://otx.alienvault.com/pulse/69bf64e1d5e06aa6207f78de","created":"2026-03-22"},{"name":"CVE Data","url":"https://otx.alienvault.com/pulse/69929b597293fe5837b9c95c","created":"2026-02-16"},{"name":"“Broken Seal” DocuSign-themed Delivery with Fileless Process Hollowing (Zeppelin/Bloat-A)","url":"https://otx.alienvault.com/pulse/698e93e1ab02db8c49e8c3ed","created":"2026-02-13"},{"name":"Thor Lite Scan - 10.7.15 - Ubuntu Scan on Archived Files","url":"https://otx.alienvault.com/pulse/664cc3c1938ed0b9abf026a2","created":"2024-05-21"},{"name":"AvosLocker Ransomware Linux Version Targets VMware ESXi Servers","url":"https://otx.alienvault.com/pulse/65707cc3f625bbc3851d61ea","created":"2023-12-06"},{"name":"AvosLocker Ransomware Linux Version Targets VMware ESXi Servers","url":"https://otx.alienvault.com/pulse/65707cbb2926882666b649ac","created":"2023-12-06"},{"name":"AvosLocker Ransomware Linux Version Targets VMware ESXi Servers","url":"https://otx.alienvault.com/pulse/65707cba0f43811a7bad3d3b","created":"2023-12-06"},{"name":"Novatech Threat Feed","url":"https://otx.alienvault.com/pulse/64b8f4e0b7008cc32a008d4f","created":"2023-07-20"}],"provenance":"machine"},"cwes":[],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-31206","tags":["vendor-advisory","patch"]},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31206","tags":["x_refsource_MISC","x_transferred"]},{"url":"https://www.zerodayinitiative.com/advisories/ZDI-21-826/","tags":["x_refsource_MISC","x_transferred"]}],"techniques":[],"reports":[{"id":"SRC-e030a140d352155c7a50","title":"RaaS AvosLocker Incident Response Analysis","publisher":"linkedin.com","url":"https://www.linkedin.com/pulse/raas-avoslocker-incident-response-analysis-fl%C3%A1vio-costa?trk=articles_directory","date":null,"mentions":[{"quote":"CVEs involved in these exploits are CVE-2021-34473, CVE-2021-31206, CVE-2021-34523, and CVE-2021-31207.","start":1949,"end":2052}]}],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-18119","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-18119","exploited":false,"exploitedSince":null,"provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":[],"flow":[],"timeline":[{"date":"2021-07-14","kind":"published","label":"Published (CVE.org)","url":"https://www.cve.org/CVERecord?id=CVE-2021-31206","provenance":"source"},{"date":"2022-01-17","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://blog.cyble.com/2022/01/17/avoslocker-ransomware-linux-version-targets-vmware-esxi-servers/","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":null},"priority":{"score":76.5,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in VulnCheck KEV"},{"name":"Recent KEV listing","points":0.0,"detail":"added 1746 days ago"},{"name":"Known ransomware use","points":10.0,"detail":"VulnCheck KEV: Known"},{"name":"EPSS percentile","points":19.26,"detail":"percentile 0.9632"},{"name":"Named in threat reports","points":3.87,"detail":"1 report"},{"name":"Public exploit code","points":0.0,"detail":"none found"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"24 pulses"},{"name":"CVSS severity","points":5.32,"detail":"base score 7.6"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}