Hackers Exploit BeyondTrust Zero-Day and Erase Security Logs to Hide Their Tracks
China-nexus UNC5221 exploited BeyondTrust Remote Support zero-day CVE-2026-102764 and wiped logs.
BeyondTrust and Mandiant say a suspected China-nexus espionage cluster exploited critical zero-day CVE-2026-102764 in BeyondTrust Remote Support on 29 August 2026, hitting one hosted instance and one self-hosted appliance, then deleted logs and tooling. BeyondTrust assesses with moderate to high confidence that the actor is UNC5221, which Mandiant calls ARMORY CASTLE and CrowdStrike tracks as WARP PANDA, previously linked to Citrix NetScaler and Ivanti Connect Secure zero-days. The intruder used a custom web shell and tunneling tool, reached full admin control within minutes, and read stored secrets. SaaS instances were patched automatically; self-hosted Remote Support and Privileged Remote Access need advisory BT26-05. Technical details are being withheld while appliances are patched.
- CVE-2026-102764 was exploited on 29 August 2026 against hosted and self-hosted Remote Support.
- BeyondTrust attributes the activity with moderate to high confidence to UNC5221, also called ARMORY CASTLE and WARP PANDA.
- The actor gained admin control, read stored secrets, used a web shell and tunnel, then deleted logs.
- SaaS was patched automatically; self-hosted Remote Support and PRA still need BT26-05.
- Mandiant warns broader exploitation of unpatched systems usually follows public disclosure.
Vulnerabilities mentionedAll →
- CVE-2024-218879.1100%Command Injection RCE in Ivanti Connect Secure and Policy Securepublished · Ivanti Connect Secure (ICS, formerly Pulse Connect Secure) KEV ransomware PoC
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A suspected China-nexus espionage group exploited a critical zero-day in BeyondTrust Remote Support, tracked as CVE-2026-102764. It then deleted logs to hide its activity.
BeyondTrust patched the flaw in advisory BT26-05 and disclosed it on October 15, 2026, alongside a Mandiant analysis.
BeyondTrust zero-day
According to research published by BeyondTrust, the actor exploited the vulnerability on August 29, 2026. It hit one BeyondTrust-hosted Remote Support instance and one self-hosted appliance.
Privileged Remote Access (PRA) shares the affected code. BeyondTrust’s testing found no way to exploit PRA, but it patched PRA as a precaution.
BeyondTrust is withholding technical details while self-hosted appliances are still being patched. SaaS instances of both products were patched automatically.
BeyondTrust assesses with moderate to high confidence that the activity belongs to UNC5221, which Mandiant now calls ARMORY CASTLE. CrowdStrike tracks the same cluster as WARP PANDA. The attribution rests on tradecraft, because the actor rotates infrastructure and tooling for every victim.
The group has previously been linked to zero-day attacks on Citrix NetScaler (CVE-2023-4966). It has also been linked to Ivanti Connect Secure (CVE-2023-46805, CVE-2024-21887 and CVE-2025-0282). Its targets include legal services, SaaS providers, business-process outsourcers, technology firms and government bodies.
BeyondTrust also suspects the actor keeps an AI model of its target products to build exploit chains. It admits it has no forensic proof of this.
| Stage | Observed behavior |
| Access | Zero-day exploit against the appliance |
| Control | Web shell used interactively over the existing web server |
| Infrastructure | Commercial VPN exits and compromised home and small-office routers |
| Escalation | Full administrative control within minutes, with reboot-surviving persistence |
| Credential theft | Reads stored secrets and uses admin access to reach downstream systems |
| Cleanup | Deletes logs and its own tooling before leaving |
Mandiant documents a custom web shell and a tunneling tool, and it published file hashes and YARA rules.
BeyondTrust’s threat hunt found the SaaS intrusion on September 28. It contained the instance 27 minutes after the compromise was identified.
Sensors fired when the actor escalated privileges, but the triage tool in a third-party detection platform closed those alerts as false positives. BeyondTrust is now working with that vendor to stop automated triage from closing high-severity signals on its own.
It released the patch on October 8, after variant analysis turned up additional attack paths.
Recommended actions include patching self-hosted Remote Support and PRA appliances immediately per BT26-05, restricting administrative interfaces to trusted networks, and limiting outbound traffic from management appliances.
Organizations should forward syslog and session events to a SIEM in near real time, since local logs may be wiped. Defenders should hunt for behavior rather than indicators, looking for admin sessions from residential or VPN addresses, unknown scripts in web directories, web service accounts spawning shells, and changes to “Jump Items” or “Teams” permissions.
Security teams should also look for log-forwarding gaps that start and end within a single session. If evidence of exploitation is found, administrators must rotate every credential the appliance stored, review new MFA registrations on privileged accounts, and image the appliance before rebuilding it.
Additionally, customers who suspect exploitation should open a Sev 1 support request citing “BT26-05”.
Mandiant warns that broad exploitation of unpatched systems typically follows public disclosure. Google Threat Intelligence Group reported that exploited vulnerabilities nearly doubled in 2026.
Attackers are weaponizing flaws faster, and AI adoption is speeding that up. Treat patch delay, appliance exposure and off-box logging as the controls that matter most.