eSentire

Zero-Days in PaperCut MF Chained to Compromise Active Directory in Education Sector

Analysts at eSentire investigated an attack that chained two zero-days in PaperCut MF, tracked as CVE-2026-81578 and CVE-2026-82078, to move from an internet-exposed print server to a domain controller in an education sector client in under two days. Attackers gained initial access through the card or badge query field, delivering malicious Java code that allowed unauthenticated configuration changes and arbitrary bytecode execution on version 24.0.2. The first stage loader reassembled payload fragments in memory, launched the next stage, and deleted its own files while remaining compatible with multiple Tomcat versions. A web shell followed, accepting commands via a custom HTTP header, reading configurations, and erasing log traces while positioning itself early in the request processing chain. The command-and-control implant was AdaptixC2, hidden inside a modified Microsoft Copilot binary downloaded from Alibaba Cloud infrastructure. Privilege escalation was achieved without passwords by locating a domain-privileged service account, stealing its access token, and relaunching the implant under those rights. On the domain controller the payload arrived via administrative share and was executed by modifying the Windows PlugPlay service, after which the legitimate path was restored to minimize traces. The operators extracted credentials from memory and registry, enabled Restricted Admin mode, used an NTLM hash for RDP access, and copied the full Active Directory database containing passwords for all domain accounts.