"The fascinating part here is that the proactive capabilities of a SIM and the resulting attack surface is explicitly defined in the technical specifications for cellular communication," said Marius Muench.
CATANA, RUN AT, and the AT-command bridge
Researchers Tomasz Piotr Lisowski and Marius Muench of the University of Birmingham, working with Fuzzware's Kristian Covic, built a toolkit called CATANA to probe what a hostile SIM could do when given proactive control. Their paper, presented at the USENIX WOOT conference in Baltimore this week, focuses on proactive SIM functionality — particularly the RUN AT capability — which lets a SIM request the execution of AT commands. As the team notes, AT commands are the long-established instruction set that "has been bossing modems around since the 1980s." Given to a hostile SIM, that standardized channel becomes an attack vector.
Scope of testing: 26 devices, startling exposure
The team tested 26 devices: 18 smartphones and eight IoT modems. They found that nine devices exposed an AT-command interface to the SIM. The IoT kit was especially permissive: seven of the eight modems the researchers tried exposed the SIM-accessible AT interface. Across that set the researchers uncovered four vulnerabilities and used the access to demonstrate multiple classes of attack.
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End the scrambleDemonstrated attacks: code execution, file theft, denial-of-service, 2G downgrade
The practical exploits the team built underline the range of consequences when a SIM can issue AT commands. On an Autel EV charger fitted with a Quectel EC25-AFX cellular module, SIM-originating commands exploited a command-injection bug in the modem's Linux-based application processor to achieve code execution. Against an Oppo Reno14 F 5G the researchers found 198 AT commands and variants available via the SIM interface; among them were commands that could power down the handset, kill its modem, or force a downgrade to 2G. That downgrade proved stubborn: toggling airplane mode, disabling the SIM, and changing the phone's network settings all failed to reverse it. Against a Quectel EG25‑G modem the team combined a malicious symbolic link with SIM-originating commands to email a targeted file to an attacker-controlled server. Overall the exploits included arbitrary file reads, denial of service, and persistent downgrade to legacy networks.
Android behavior, CVE-2025-48618, and disclosure timeline
The researchers also found that vulnerable versions of Android allowed a hostile SIM to invoke the standardized LAUNCH BROWSER command and open an attacker-controlled website without user interaction — even while the phone was locked. Google tracked that issue as CVE-2025-48618 and patched Android 13 through 16 in December 2025. The research team disclosed their findings to Google, Oppo, Quectel, Semtech, and Qualcomm in March, and informed the GSMA in May.
Vendor and standards responses: Qualcomm, GSMA, and patches
Following disclosure, Qualcomm produced a hardened configuration that disables the SIM AT interface by default. The GSMA is tracking the broader issue under CVD-2026-0122. The researchers recommend a more far-reaching fix: retiring RUN AT and other proactive SIM functionality they judge risky. They note that modern smartphones appear largely to have "got the memo" about limiting SIM-originated command exposure, while the IoT ecosystem still shows lingering vulnerabilities.
What this means for technologists, procurement teams, and end users
- Technologists and security teams: the work shows that proactive SIM functionality is specification-compliant yet dangerous; teams should prioritize audits of SIM-exposed AT interfaces in modems and device stacks, especially in IoT modems where seven of eight tested units exposed the interface.
- Procurement and enterprise IoT operators: the examples — including Quectel EC25-AFX and EG25‑G modules and an Autel EV charger — flag that supplier configuration and module firmware matter. Buyers should demand evidence that SIM AT interfaces are disabled or hardened, and track vendor mitigations such as Qualcomm's hardened configuration.
- End users and device maintainers: the attacks require control of the SIM itself — via compromised SIM software, physical tampering, abuse of remote SIM administration, or supply-chain compromise — so SIM provenance and operator provisioning controls are relevant risk points to watch.
The researchers' bottom-line recommendation is stark and specific: retire RUN AT and similarly risky proactive SIM capabilities. With Google patches, Qualcomm configuration changes, and the GSMA tracking the problem, remedial attention has started. But the demonstration against IoT modems and an EV charger shows that specification-compliant mechanisms can still be weaponized where legacy behaviors remain in place — and the researchers conclude the IoT world still has some catching up to do.
