{"id":"CVE-2021-21985","published":"2021-05-26T15:15:07Z","modified":"2026-08-12T05:17:36Z","title":"VMware vCenter Server Improper Input Validation Vulnerability","vendor":"VMware","product":"vCenter Server","tier":"core","eol":null,"description":{"text":"The vSphere Client (HTML5) contains a remote code execution vulnerability due to lack of input validation in the Virtual SAN Health Check plug-in which is enabled by default in vCenter Server. A malicious actor with network access to port 443 may exploit this issue to execute commands with unrestricted privileges on the underlying operating system that hosts vCenter Server.","provenance":"source","from":"NVD"},"summary":{"text":"The vSphere Client (HTML5) in VMware vCenter Server contains a remote code execution flaw caused by missing input validation in the Virtual SAN Health Check plug-in, which is enabled by default. An attacker with network access to port 443 and no authentication or user interaction can execute commands with unrestricted privileges on the operating system hosting vCenter Server.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-29T07:53:36Z"},"cvss":{"score":9.8,"severity":"CRITICAL","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.99999,"percentile":0.99992,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2021-11-03","dueDate":"2021-11-17","ransomware":true,"requiredAction":"Apply updates per vendor instructions.","notes":"https://nvd.nist.gov/vuln/detail/CVE-2021-21985","provenance":"source"},"vulncheckKev":{"dateAdded":"2021-06-04","exploitedFirstSeen":"2021-06-04","ransomware":true,"evidence":[{"url":"https://cisa.gov/news-events/alerts/2021/06/04/unpatched-vmware-vcenter-software","date":"2021-06-04"},{"url":"https://www.cisa.gov/news-events/cybersecurity-advisories/aa21-209a","date":"2021-08-20"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2021-11-03"},{"url":"https://www.tenable.com/blog/contileaks-chats-reveal-over-30-vulnerabilities-used-by-conti-ransomware-affiliates","date":"2022-03-24"},{"url":"https://cybersecurityworks.com/howdymanage/uploads/file/RansomwareUpdate%20Report%202022%20Q1.pdf","date":"2022-04-12"},{"url":"https://cisa.gov/news-events/alerts/2022/04/27/2021-top-routinely-exploited-vulnerabilities","date":"2022-04-28"},{"url":"https://cisa.gov/news-events/cybersecurity-advisories/aa22-117a","date":"2022-04-28"},{"url":"https://ransomware.org/blog/initial-access-vectors-for-ransomware/","date":"2022-05-13"},{"url":"https://static.tenable.com/marketing/whitepapers/Whitepaper-Ransomware_Ecosystem.pdf","date":"2022-06-22"},{"url":"https://www.securin.io/articles/all-about-conti-ransomware/","date":"2022-06-29"}],"evidenceTotal":829,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"},{"name":"Actively_Exploited_Kev | Oct 19, 2026","url":"https://otx.alienvault.com/pulse/6ad4dda174e5797d0bd238b7","created":"2026-10-18"},{"name":"Actively_Exploited_Kev | Oct 18, 2026","url":"https://otx.alienvault.com/pulse/6ad38c22e1848f8189d1c121","created":"2026-10-17"}],"provenance":"machine"},"cwes":[{"id":"CWE-918","name":"Server-Side Request Forgery"},{"id":"CWE-20","name":"Improper Input Validation"},{"id":"CWE-470","name":"Use of Externally-Controlled Input to Select Classes or Code"}],"references":[{"url":"http://packetstormsecurity.com/files/162812/VMware-Security-Advisory-2021-0010.html","tags":["Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/163487/VMware-vCenter-Server-Virtual-SAN-Health-Check-Remote-Code-Execution.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"https://www.vmware.com/security/advisories/VMSA-2021-0010.html","tags":["Vendor Advisory"]},{"url":"http://packetstormsecurity.com/files/162812/VMware-Security-Advisory-2021-0010.html","tags":["Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/163487/VMware-vCenter-Server-Virtual-SAN-Health-Check-Remote-Code-Execution.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"https://www.vmware.com/security/advisories/VMSA-2021-0010.html","tags":["Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21985","tags":["US Government Resource"]}],"techniques":[{"id":"T1190","name":"Exploit Public-Facing Application","tactics":["initial-access"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: network-reachable web client exploited remotely over HTTPS","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"A malicious actor with network access to port 443 may exploit this issue","start":193,"end":265}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1059","name":"Command and Scripting Interpreter","tactics":["execution"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: arbitrary command execution on host OS","mappingType":"primary_impact","evidence":[{"from":"description","quote":"to execute commands with unrestricted privileges on the underlying operating system","start":266,"end":349}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-9156","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-9156","exploited":true,"exploitedSince":"2021-11-03","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":10,"skipped":0,"earliest":"2021-05-27","earliestUrl":"https://github.com/bigbroke/CVE-2021-21985","repos":[{"name":"alt3kx/CVE-2021-21985_PoC","url":"https://github.com/alt3kx/CVE-2021-21985_PoC","stars":214,"created":"2021-05-29"},{"name":"xnianq/cve-2021-21985_exp","url":"https://github.com/xnianq/cve-2021-21985_exp","stars":115,"created":"2021-06-03"},{"name":"testanull/Project_CVE-2021-21985_PoC","url":"https://github.com/testanull/Project_CVE-2021-21985_PoC","stars":28,"created":"2021-06-05"},{"name":"sknux/CVE-2021-21985_PoC","url":"https://github.com/sknux/CVE-2021-21985_PoC","stars":3,"created":"2021-11-09"},{"name":"onSec-fr/CVE-2021-21985-Checker","url":"https://github.com/onSec-fr/CVE-2021-21985-Checker","stars":2,"created":"2021-06-01"}]},"metasploit":[{"name":"VMware vCenter Server Virtual SAN Health Check Plugin RCE","module":"exploit/linux/http/vmware_vcenter_vsan_health_rce","type":"exploit","disclosureDate":"2021-05-25","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/http/vmware_vcenter_vsan_health_rce.rb"}],"nuclei":[{"id":"CVE-2021-21985","name":"VMware vSphere Client (HTML5) - Remote Code Execution","severity":"critical","path":"http/cves/2021/CVE-2021-21985.yaml","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-21985.yaml"}],"first":{"date":"2021-05-25","source":"Metasploit","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/http/vmware_vcenter_vsan_health_rce.rb"},"provenance":"source"},"exploitRefs":["http://packetstormsecurity.com/files/163487/VMware-vCenter-Server-Virtual-SAN-Health-Check-Remote-Code-Execution.html","http://packetstormsecurity.com/files/162812/VMware-Security-Advisory-2021-0010.html"],"flow":[{"stage":"exploitation","techniques":["T1190"],"provenance":"ai"},{"stage":"primary","techniques":["T1059"],"provenance":"ai"}],"timeline":[{"date":"2021-05-25","kind":"exploit-public","label":"First public exploit: Metasploit; later: PoC-in-GitHub 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exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-9156","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":"Metasploit","daysToKev":161},"priority":{"score":79.9,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":0.0,"detail":"added 1974 days ago"},{"name":"Known ransomware use","points":10.0,"detail":"CISA KEV and VulnCheck KEV: Known"},{"name":"EPSS percentile","points":20.0,"detail":"percentile 0.9999"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 NVD reference tagged Exploit; 1 NVD exploit link; 10 PoC-in-GitHub repos; 1 Metasploit module; 1 nuclei template"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":6.86,"detail":"base score 9.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}