Verizon's VoLTE IMS network transmits SIP signaling without integrity protection…

Verizon's VoLTE IMS network transmits SIP signaling without integrity protection, allowing on-path attackers to intercept and manipulate calls, messages, and emergency routing.

Security researchers from Kyung Hee University discovered that Verizon's Voice over LTE (VoLTE) deployments operate without negotiated SIP integrity protection, violating 3GPP TS 33.203 and GSMA IR.92 standards. Testing revealed that SIP signaling—including registration, call setup, and messaging—travels without IPsec ESP encapsulation and lacks required Security-Client, Security-Server, and Security-Verify headers. This pattern persisted across multiple devices, operating systems, and network conditions, indicating a systemic network configuration issue rather than isolated incidents.

The absence of integrity protection allows on-path attackers to intercept, replay, or modify SIP messages undetected, enabling call hijacking, caller ID spoofing, denial-of-service attacks, and manipulation of emergency call routing. While Apple released iOS carrier bundle 26.5 on May 11, 2026, containing IMS IPsec-related settings, and Verizon initially acknowledged the issue, the company has ceased coordination efforts and provided no verifiable evidence of remediation. The operational status of any deployed protections remains unconfirmed.

Remediation requires Verizon to enable SIP security negotiation and IPsec ESP protection in its IMS core infrastructure, paired with correct carrier configurations on user devices. Organizations requiring high-assurance voice communications should treat VoLTE signaling on Verizon's network as untrusted until successful SIP security negotiation and ESP-protected traffic can be independently verified.

Source reporting: https://kb.cert.org/vuls/id/615987