The Descent Through the Trust Stack: A 2025 Breach Scenario Reconstructed from Pattern-True Artifacts

This case study reconstructs a plausible 2025 breach scenario using five actively exploited vulnerabilities (CVE-2025-7775, CVE-2025-64446, CVE-2025-53770, CVE-2025-61882, CVE-2025-55182) to demonstrate a pattern that conventional incident response consistently fails to recognize: trust-stack descent. Rather than lateral movement across systems, the adversary moves downward through architectural layers—from perimeter to identity to collaboration to operational core to application substrate—inheriting each layer's authority as they go. Each compromised layer continues to function normally from the perspective of the defenders, because the attacker does notviolate the layer's trust model; they absorb it. The breach is complete before the first alert fires. Discovery occurs not through detection but through contradiction: temporal inconsistencies between systems whose logs should agree but no longer do. The trust-stack descent model is independently validated by CVE-2026-20127, a CVSS 10.0 Cisco SD-WAN authentication bypass disclosed on February 25, 2026, under active zero-day exploitation since 2023, which conforms precisely to the inherited-authority pattern described herein. This case study argues that the fundamental unit of breach analysis is not the vulnerability, the indicator of compromise, or the lateral path—it is the trust assumption, and that breaches propagate by collapsing trust assumptions sequentially across architectural layers.