Description

The China-linked cyber espionage group Armory Castle, also tracked as UNC5221 and Warp Panda, exploited a newly disclosed zero-day vulnerability in BeyondTrust Remote Support in late August 2026. Tracked as CVE-2026-102764, the flaw has a CVSS score of 9.3 and stems from improper origin validation in an internal messaging component, potentially allowing remote attackers to perform file operations on affected appliances. BeyondTrust confirmed that patches were deployed to all Remote Support SaaS customers by October 9, 2026. Self-hosted customers running versions 24.3.1 through 26.2.3 are advised to install patch BT26-05-RS, while users of older versions must upgrade to a supported release. According to BeyondTrust, Armory Castle exploited the vulnerability against a single self-hosted appliance on August 29, 2026. The company launched an investigation on September 27 after another security device provider's successful exploitation became public. The group, active since October 2023, has previously exploited zero-day vulnerabilities in Citrix NetScaler and Ivanti Connect Secure appliances to target government agencies, technology companies, legal services, SaaS providers, and business-process outsourcers. Researchers assess that the group selectively targets high-value software and expands exploitation once vulnerabilities become publicly known. Google-owned Mandiant reported that successful exploitation led to the deployment of SAWFLY, a lightweight PHP web shell used for remote access and encrypted command-and-control communications. Attackers leveraged VPN exit nodes and compromised home and small-office routers to conceal their activity. They escalated privileges by modifying system files, attempted to steal credentials from BeyondTrust's secrets database, and abused administrator accounts to access downstream systems through configured Jump Items. The attackers also used BARECLAW, a custom SOCKS5 tunneler, modified HAProxy configuration to expose it externally, and deleted system, web server, and application logs to hinder detection. Mandiant and Google Threat Intelligence Group warned that the intrusion demonstrated deep knowledge of BeyondTrust appliance internals. Any internet-accessible appliance running a vulnerable version during the exploitation window should be treated as potentially compromised until thoroughly investigated. Organizations should apply the relevant patches, review access logs and credentials, investigate suspicious remote sessions, and assess downstream systems for signs of lateral movement or data exfiltration.