Silk Typhoon (HAFNIUM), a Chinese 🇨🇳 state APT, has evolved from on-prem Exchange exploitation to cloud-native supply chain attacks, most recently abusing CVE-2025-3928 in Commvault's Azure-hosted M365 backup SaaS to pivot into downstream customer tenants. - Initial access spans three vectors: CVE-2025-3928 (zero-day in Commvault Web Server, T1190), stolen API keys from privileged cloud vendors (T1195), and leaked corporate credentials found on public repos like GitHub (T1078.004). The Commvault campaign gave them client secrets for Metallic M365 backups, opening direct paths into customer M365 environments via hijacked service principals. - Lateral movement pivots from on-prem to cloud by targeting Entra Connect servers (T1210, T1078.002), enabling privilege sync between Active Directory and Entra ID. Credential dumping and key vault theft support pass-the-hash moves (T1550.002) into Azure. - Persistence relies on adding passwords to existing consented service principals or creating new Entra ID applications named to mimic legitimate Office 365 services (T1098.001, T1036). Web shells handle C2 on compromised Azure VMs (T1505.003). - Collection targets email via EWS and MSGraph APIs, plus SharePoint (T1213.002) and OneDrive (T1213.003), all through OAuth apps with admin consent, a low-noise, API-native exfiltration path that bypasses many endpoint controls. #DFIR_Radar
Post summary
Silk Typhoon (HAFNIUM) is actively exploiting CVE-2025-3928 in Commvault’s cloud‑hosted M365 backup SaaS to pivot into downstream customer tenants via stolen credentials and lateral movement.