Operators linked to the Qilin ransomware have exploited an authentication bypass flaw in Palo Alto Networks PAN-OS to breach corporate networks and encrypt systems. The attacks, first observed in June 2026, began through the GlobalProtect VPN service installed on Palo Alto firewalls.
Tracked as CVE-2026-0257, the vulnerability allows attackers to circumvent authentication and establish VPN sessions without valid credentials. Exploitation requires the use of crafted authentication-replacement cookies combined with specific certificate configurations.
After obtaining initial access, the intruders collected credentials from Windows and Active Directory, including data extracted from LSASS processes and NTDS databases. Compromised administrative accounts were then used to reach servers, workstations, and backup systems.
Lateral movement was conducted primarily via PsExec and administrative shares. Additional tools observed in some intrusions included AnyDesk, Ngrok, LogMeIn, NetExec, and various network scanners employed to expand and maintain access.
Prior to encryption, the operators disabled Microsoft Defender real-time protection and cleared event logs. The ransomware payload was stored as win.exe, typically inside the C:\PerfLogs\ directory. Some victims experienced only partial encryption of their systems.
The flaw impacts vulnerable versions of PAN-OS 10.2, 11.1, 11.2, and 12.1, as well as certain editions of Prisma Access. Panorama and Cloud NGFW are not affected. The vendor has confirmed limited exploitation attempts against unpatched devices.
