UNC6603
UNC6603 is a China-nexus espionage threat actor observed exploiting the React Server Components vulnerability CVE-2025-55182 ("React2Shell") for initial access. Reporting states the group deployed an updated version of the Go-based HISONIC backdoor, and that this malware was designed to use legitimate cloud services including Cloudflare Pages and GitLab to retrieve encrypted configuration and blend in with normal network activity. Additional reporting notes HISONIC traffic communicating through legitimate services such as Cloudflare. UNC6603 has been associated with delivery of HISONIC during React2Shell exploitation and was specifically reported targeting cloud infrastructure, including AWS and Alibaba Cloud instances, in the Asia-Pacific region. Known alias in the provided content: UNC6603.
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Targeting
Who, where, and (when attributed) which flag flies behind the operation. Pulled from open-source reporting and Mallory's analyst review.
Where they're from
Attributed origin per open-source reporting.
- CN
Tradecraft
3 distinct techniques observed across reporting, grouped by tactic. Hover any cell for the evidence excerpt; click through for MITRE's full description.
Associated malware families
4 malware families attributed to this actor across reporting.
Associated vulnerabilities
1 CVE this actor has used in observed campaigns. 1 of them exploited in the wild.
Recent activity
16 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Referenced as a reported user of the HISONIC backdoor; tooling consistent with post-exploitation persistence/remote access after React2Shell (CVE-2025-55182) exploitation.
Listed as a threat actor associated in the report’s aggregated section with exploitation activity around React2Shell (CVE-2025-55182) and related RSC/Next.js vulnerabilities.
Named in an aggregated list of actors associated with React2Shell (CVE-2025-55182) exploitation activity (UNC-style naming suggests an uncategorized cluster).
China-nexus threat actor exploiting CVE-2025-55182 to deploy updated HISONIC backdoor.
The version that knows your environment.
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.