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UNK_DoubleCheck is an espionage-focused threat activity cluster tracked by Proofpoint, observed targeting a Vietnamese manufacturing organization beginning on September 2, 2026. Its country of origin and state affiliation have not been established. The cluster used spearphishing messages sent from a compromised Southeast Asian government email account, with a vaccination-appointment lure directing recipients to actor-controlled Cloudflare Workers infrastructure hosting the BlueMoon exploit kit. BlueMoon combines Chromium V8 exploitation and sandbox escape with Windows local privilege escalation to compromise vulnerable Windows systems. Its chain includes CVE-2026-85046 and CVE-2026-85880, and exploits the gap between publicly available upstream Chromium fixes and their deployment in stable browsers. The kit fingerprints the host before attempting privilege escalation and injects code into the parent Chrome broker process to launch subsequent payloads. UNK_DoubleCheck used an obfuscated BlueMoon variant to initiate a DLL-sideloading chain that loaded a Rust executable into memory. The Rust loader subsequently retrieved and executed a second DLL-sideloading pair from Cloudflare R2. Although UNK_DoubleCheck shared BlueMoon with other espionage clusters, including TA412, UNK_LateNight, and UNK_QuietRacket, it is tracked as a distinct activity cluster; shared exploit use does not establish common ownership or national attribution.
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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.
19 distinct techniques observed across reporting, grouped by tactic. Hover any cell for the evidence excerpt; click through for MITRE's full description.
1 malware family attributed to this actor across reporting.
3 CVEs this actor has used in observed campaigns. 3 of them exploited in the wild.
CVE-2026-85046 is one of two remote-code-execution defects in the JavaScript engine for Chromium-based browsers. UTA0565 exploited it as part of a triple-link zero-day chain between September 3 and 4, before disclosure or patching.
CVE-2026-85880 is a privilege-escalation zero-day in Windows Advanced Local Procedure Call that Microsoft disclosed on September 8. UTA0565 exploited it in a triple-link chain with two Chromium-based browser RCE flaws.
CVE-2026-87491 is one of two remote-code-execution defects in the JavaScript engine for Chromium-based browsers. UTA0565 exploited it as part of a triple-link zero-day chain between September 3 and 4, before disclosure or patching.
20 indicators attributed to this actor: domains, IPs, hashes, and other artifacts pulled from reporting. View more in app.
17 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Previously attributed by Proofpoint as conducting attacks involving the same chained zero-day vulnerabilities discussed in this reference.
Targeted a Vietnamese manufacturing organization through a compromised government email account, deploying a DLL-side-loading chain that loads a Rust executable.
Unattributed espionage cluster that used BlueMoon against a Vietnamese manufacturing organization and deployed an in-memory Rust executable through a DLL-sideloading infection chain.
Неатрибутированная группа, применившая BlueMoon против производственной компании во Вьетнаме.
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.