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UNC5337 is a suspected China-nexus cyber espionage cluster associated with exploitation of Ivanti Connect Secure VPN appliances and deployment of the SPAWN malware ecosystem. The actor has been observed compromising Ivanti edge devices from at least January 2024 and has been linked to exploitation of multiple Ivanti vulnerabilities, including CVE-2023-46805, CVE-2024-21887, and later CVE-2025-0282. Reporting also places UNC5337 activity within a broader China-linked intrusion set overlapping or potentially converging with UNC5221, with some assessments judging the two to be the same actor or closely related clusters. UNC5337’s tradecraft centers on initial access through edge-device exploitation followed by stealthy post-exploitation on the appliance and, in some cases, pivoting into internal networks. Malware associated with the cluster includes SPAWNSNAIL, SPAWNMOLE, SPAWNANT, and SPAWNSLOTH; later reporting also ties the actor to the broader SPAWN ecosystem and updated SPAWN variants used in Ivanti-focused operations. The toolkit supports persistence, tunneling, backdoor access, and log wiping, indicating strong defense-evasion and post-exploitation capability. UNC5337 has also been associated with delivery of additional tooling such as DRYHOOK and PHASEJAM during exploitation of Ivanti appliances. The actor has targeted organizations globally through widespread exploitation of internet-facing VPN infrastructure. Confirmed victim geography includes organizations in Australia, Austria, France, Japan, South Korea, Spain, and the United States. Reported targeting spans government, financial institutions, telecommunications, automotive, and chemical organizations, consistent with strategic intelligence collection rather than financially motivated intrusion. Operational characteristics include use of custom malware tailored for network appliances, layered command-and-control, evasion of monitoring, and log wiping that complicates forensic reconstruction.
Mallory correlates actor tradecraft and target patterns against your stack, your sector, and your geography. See overlap before they land.
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.
11 distinct techniques observed across reporting, grouped by tactic. Hover any cell for the evidence excerpt; click through for MITRE's full description.
8 malware families attributed to this actor across reporting.
3 additional families tracked in Mallory.
4 CVEs this actor has used in observed campaigns. 4 of them exploited in the wild.
CVE-2025-0282 (CVSS: 9.0) is a stack-based buffer overflow vulnerability that allows unauthenticated remote attackers to execute arbitrary code. As per the advisory, CVE-2025-0282 has been exploited in the wild, affecting a limited number of Connect Secure devices.
Since the initial disclosure of CVE-2023-46805 and CVE-2024-21887 on Jan. 10, 2024... Mandiant is tracking multiple clusters of activity exploiting CVE-2023-46805, CVE-2024-21887, and CVE-2024-21893... UNC5337 is suspected to exploit CVE-2023-46805 (authentication bypass) and CVE-2024-21887 (command injection) for infecting Ivanti Connect Secure appliances.
Since the initial disclosure of CVE-2023-46805 and CVE-2024-21887 on Jan. 10, 2024... Mandiant's previous blog post details zero-day exploitation of CVE-2024-21893 and CVE-2024-21887... UNC5337 is suspected to exploit CVE-2023-46805 (authentication bypass) and CVE-2024-21887 (command injection) for infecting Ivanti Connect Secure appliances.
Similarly, CVE-2025-22457 is also attributed to a stack-based buffer overflow weakness. This vulnerability impacts a range of Ivanti products, including Pulse Connect Secure 9.1x and Ivanti Connect Secure 22.7R2.5 and earlier... Ivanti released a patch for this vulnerability on February 11, 2025.
3 indicators attributed to this actor: domains, IPs, hashes, and other artifacts pulled from reporting. View more in app.
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
UNC5337 is a China-nexus threat actor known for exploiting edge-appliance vulnerabilities (notably Ivanti Connect Secure CVE-2025-0282/0283) to gain access to networks, leading to operational downtime and requiring extensive remediation.
China-nexus cyber espionage activity exploiting Ivanti Connect Secure (ICS) CVE-2025-0282 (as a zero-day) to deploy the SPAWN malware ecosystem and related tooling (DRYHOOK, PHASEJAM).
China-linked cyber espionage activity targeting Ivanti Connect Secure VPN appliances by exploiting critical stack buffer overflow vulnerabilities to gain remote code execution and deploy the SPAWN* malware toolkits (e.g., SPAWNCHIMERA modules) for persistence, tunneling, backdoor access, and log wiping.
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.