{"cveID":"CVE-2021-27065","vendorProject":"Microsoft","product":"Exchange Server","vulnerabilityName":"Microsoft Exchange Server Remote Code Execution Vulnerability","dateAdded":"2021-11-03","shortDescription":"Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.","requiredAction":"Apply updates per vendor instructions.","dueDate":"2022-05-03","knownRansomwareCampaignUse":"Known","notes":"Reference CISA's ED 21-02 (https://www.cisa.gov/news-events/directives/ed-21-02-mitigate-microsoft-exchange-premises-product-vulnerabilities) for further guidance and requirements. Note: The due date for addressing this vulnerability aligns with the requirements outlined in ED 21-02. https://nvd.nist.gov/vuln/detail/CVE-2021-27065","cwes":["CWE-39"],"year":2021,"state":"mapped","stale_reasons":[],"mappings":[{"domain":"enterprise","cve":"CVE-2021-27065","technique":"T1190","technique_name_at_mapping":"Exploit Public-Facing Application","mapping_type":"exploitation_technique","capability_group":"code_execution","comments":"CVE-2021-26858, part of Proxy Logon, is a post-authentication arbitrary file write vulnerability in Exchange. CVE-2021-26858 and CVE-2021-27065 are similar post-authentication arbitrary write file vulnerabilities in Exchange. An attacker, authenticated either by using CVE-2021-26855 or via stolen admin credentials, could write a file to any path on the server.","references":["https://www.microsoft.com/en-us/security/blog/2021/03/02/hafnium-targeting-exchange-servers/"],"status":"complete","source_file":"kev-07.28.2025_attack-16.1-enterprise.json","attack_version":"16.1","kev_snapshot":"07/28/2025"},{"domain":"enterprise","cve":"CVE-2021-27065","technique":"T1505.003","technique_name_at_mapping":"Web Shell","mapping_type":"primary_impact","capability_group":"code_execution","comments":"CVE-2021-26858, part of Proxy Logon, is a post-authentication arbitrary file write vulnerability in Exchange. CVE-2021-26858 and CVE-2021-27065 are similar post-authentication arbitrary write file vulnerabilities in Exchange. An attacker, authenticated either by using CVE-2021-26855 or via stolen admin credentials, could write a file to any path on the server.","references":["https://www.microsoft.com/en-us/security/blog/2021/03/02/hafnium-targeting-exchange-servers/"],"status":"complete","source_file":"kev-07.28.2025_attack-16.1-enterprise.json","attack_version":"16.1","kev_snapshot":"07/28/2025"}],"techniques":[{"id":"T1190","domains":["enterprise"],"in_current_bundle":true,"live":true,"name_now":"Exploit Public-Facing Application","name_at_mapping":"Exploit Public-Facing Application","renamed":false,"revoked_by":null,"mapping_types":["exploitation_technique"],"sigma_rule_count":149,"has_detection_strategy":true},{"id":"T1505.003","domains":["enterprise"],"in_current_bundle":true,"live":true,"name_now":"Web Shell","name_at_mapping":"Web Shell","renamed":false,"revoked_by":null,"mapping_types":["primary_impact"],"sigma_rule_count":35,"has_detection_strategy":true}],"mapping_types":["exploitation_technique","primary_impact"],"has_exploitation_technique":true,"mapping_attack_versions":["16.1"],"mapping_domains":["enterprise"],"sigma_coverage":"full","sigma_rules_tagged_cve":[],"added_after_mapping_snapshot":false,"_source":"kevmap","_built":"2026-08-23 05:47 UTC","_attack_version":"19.2"}