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UNC2640 is a Mandiant temporary activity cluster associated with exploitation of the 2021 Microsoft Exchange ProxyLogon vulnerability chain affecting on-premises Exchange Server. It was tracked alongside UNC2639 and UNC2643 during the wave of intrusions that used CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065 to achieve remote code execution and deploy web shells for persistent access. Observed activity attributed to this cluster included exploitation of vulnerable Exchange servers, creation of web shells through Exchange-related processes, operation under highly privileged contexts, and follow-on post-compromise actions. Reported behaviors included reconnaissance for endpoint security products, credential gathering, lateral movement, and broader post-exploitation on compromised environments. The cluster was identified during investigations involving victims such as U.S.-based retailers, local governments, a university, and an engineering firm, with possible related activity affecting a Southeast Asian government and a Central Asian telecommunications entity. UNC2640 is a preliminary uncategorized cluster designation rather than a fully established intrusion set. The broader exploitation activity was publicly linked by Microsoft to the China-linked state-sponsored actor HAFNIUM, but the supplied facts do not independently establish UNC2640 itself as a distinct nation-state group beyond its role as one of several clusters observed during the ProxyLogon exploitation wave.
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Who, where, and (when attributed) which flag flies behind the operation. Pulled from open-source reporting and Mallory's analyst review.
Sectors the actor has been observed targeting.
Geographies tied to known operations.
Attributed origin per open-source reporting.
4 distinct techniques observed across reporting, grouped by tactic. Hover any cell for the evidence excerpt; click through for MITRE's full description.
4 CVEs this actor has used in observed campaigns. 4 of them exploited in the wild.
CVE-2021-26855 (CVSS 9.1) is a server-side request forgery (SSRF) vulnerability in Exchange that allows the attacker to send arbitrary HTTP requests and authenticate as the Exchange server.
CVE-2021-26857 (CVSS 7.8) is an insecure deserialization vulnerability in the Unified Messaging service. Exploiting this vulnerability gives the threat actor the ability to run code as SYSTEM on the Exchange server.
CVE-2021-26858 (CVSS 7.8) is a post-authentication arbitrary file write vulnerability in Exchange. If the threat actor first authenticates with the Exchange server they could then use this vulnerability to write a file to any path on the server.
CVE-2021-27065 (CVSS 7.8) is a post-authentication arbitrary file write vulnerability in Exchange. If the threat actor first authenticates with the Exchange server they could then use this vulnerability to write a file to any path on the server.
2 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Match sector + geo + tech-stack targeting against your real footprint.
Every observed MITRE ATT&CK technique, grouped by tactic.
Families this actor is known to deploy, with IOCs and behavior.
CVEs this actor has used in known campaigns.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Domains, IPs, and hashes tied to this actor, refreshed continuously.