Written by: Chester Sng, Pete Boonyakarn, Logeswaran Nadarajan, Lukasz Lamparski Introduction In early 2026, Mandiant identified a threat actor targeting SD-WAN infrastructure at a service provider. After gaining initial access, the threat actor exploited a zero-day vulnerability ( CVE-2026-20245 ) in Cisco Catalyst SD-WAN to escalate privileges from a compromised administrative account to root-level access. The vulnerability stems from the device’s file upload feature lacking the ability to properly filter malicious data. Throughout the intrusion, to maintain operational security and avoid detection, the threat actor consistently employed anti-forensic techniques, selectively deleting and r