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UNC6603 is a China-nexus cyber-espionage threat cluster associated with exploitation of the React Server Components remote code execution vulnerability CVE-2025-55182, also known as React2Shell. The cluster has been observed using the vulnerability for initial access and then deploying an updated version of the Golang-based HISONIC backdoor for post-compromise access and persistence. HISONIC is designed to blend malicious traffic with legitimate network activity by leveraging trusted cloud services for configuration retrieval and communications. UNC6603 has been linked to targeting cloud infrastructure, specifically AWS and Alibaba Cloud instances, in the Asia-Pacific region. The cluster is part of a broader set of China-aligned intrusion activity exploiting newly disclosed internet-facing vulnerabilities to establish footholds on exposed systems and support follow-on espionage operations.
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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.
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 malware families attributed to this actor across reporting.
1 CVE this actor has used in observed campaigns. 1 of them exploited in the wild.
1 indicator 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.
Referenced as a threat actor reportedly associated with the HISONIC backdoor, which was found installed in the incident.
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).
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.