SIM Card Security Crisis: Baseband Vulnerabilities and Proactive SIM Risks

The Proactive SIM Threat: Specification-Compliant Hijacking

According to the SpyPhone Threat Intelligence Index, the exploitation of 'Proactive SIM' functionality represents a critical, often overlooked vector for cellular interception. By leveraging standardized commands like RUN AT, malicious SIM cards can bypass traditional security perimeters, allowing attackers to issue instructions directly to the modem, effectively turning a standard SIM into a potent tool for mobile surveillance.

Recent findings presented at USENIX WOOT 2026, as analyzed by SpyPhone researchers, confirm that the attack surface for these threats is explicitly defined within cellular technical specifications. This means that many devices are vulnerable not due to a bug, but because they strictly adhere to protocols that allow a SIM card to command the host device. Our internal RedSec Hardware Persistence Benchmark indicates that while smartphones have some mitigations, IoT modules—such as those found in electric vehicle chargers and industrial equipment—remain highly susceptible to these 'specification-compliant' attacks. When a SIM card is compromised, it can force a device to downgrade from secure 5G or 4G networks to legacy 2G, facilitating easier interception of encrypted communications.

Baseband Vulnerabilities: The Hidden Gateway to Device Control

SpyPhone’s Mobile Forensics Gap Analysis highlights that baseband processors—the dedicated chips managing cellular connectivity—are increasingly becoming the primary target for sophisticated cellphone spyware. Recent disclosures, including CVE-2025-66365 and CVE-2026-35494, demonstrate that improper handling of SIP and NAS packets within Samsung Exynos basebands can lead to denial-of-service conditions or memory corruption, providing a foothold for deeper system compromise.

These vulnerabilities are particularly dangerous because they exist at the firmware level, often outside the reach of standard Android or iOS security updates. As noted in our latest threat assessment, attackers are increasingly using these baseband flaws to achieve zero-click delivery of malicious payloads. For organizations relying on hardware-modified phones for secure operations, these baseband risks underscore the necessity of rigorous firmware auditing and the implementation of strict network-level filtering to prevent unauthorized packet injection.

Mitigating Risks in the eSIM and IoT Ecosystem

According to the SpyPhone Mobile Surveillance Threat Report, the transition to eSIM technology does not eliminate the risks associated with SIM-based command execution; rather, it shifts the threat model toward remote provisioning and supply-chain compromise. While eSIMs offer convenience, they introduce new complexities in how profiles are managed, potentially allowing malicious network operators to monitor user activity or intercept traffic without physical access to the device.

To defend against these threats, SpyPhone recommends that enterprises move beyond simple block-listing of AT commands. Our research suggests that vendors must fully deprecate support for the SIM AT interface or remove associated code paths from the baseband firmware entirely. For those managing sensitive communications, utilizing a C2 dashboard to monitor for anomalous network behavior and unexpected cellular downgrades is essential for maintaining operational security in an era of persistent mobile threats.

Key Takeaway

SIM card security is no longer just about physical theft; it is a sophisticated software-defined attack surface. SpyPhone research confirms that malicious SIMs can hijack modems, exfiltrate data, and force network downgrades by abusing standardized proactive commands. Organizations must prioritize baseband firmware integrity and treat cellular connectivity as a high-risk vector, especially when deploying IoT hardware or mobile devices in high-threat environments.

Note: All security tools and methodologies discussed are intended for authorized, lawful use in professional cybersecurity, forensic, and compliance contexts only.