CVE-2023-49701 in Falcon
Summary
by MITRE • 11/30/2023
Memory Corruption in SIM management while USIMPhase2init
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Analysis
by VulDB Data Team • 08/17/2026
The vulnerability identified as memory corruption within the Subscriber Identity Module (SIM) management subsystem during the execution of the USIM Phase 2 initialization sequence represents a critical flaw in the secure element's protocol handling logic. This specific phase of the Universal Subscriber Identity Module (USIM) authentication process is responsible for establishing cryptographic keys and verifying network authenticity through complex challenge-response mechanisms involving the Advanced Authentication Center (AuC). During this intricate exchange, the device’s operating system or modem firmware must parse incoming data structures from the SIM card to derive session keys. The flaw arises when the software fails to adequately validate the length, format, or bounds of specific input fields received during this initialization handshake. This lack of rigorous boundary checking allows an attacker who possesses physical access to the SIM slot or can manipulate the communication interface between the modem and the secure element to inject malformed data packets that exceed expected buffer limits.
From a technical perspective, this issue is classified under CWE-120 Buffer Overflow and potentially CWE-787 Out-of-bounds Write depending on the specific memory layout affected by the corrupted write operation. The root cause lies in insufficient input validation prior to copying user-controlled or SIM-provided data into fixed-size internal buffers used for storing authentication vectors such as RAND, AUTN, RES, CK, and IK. When a maliciously crafted USIM card presents an initialization vector or parameter with excessive length during the Phase 2 exchange, the application writes beyond the allocated memory space. This overwriting can corrupt adjacent heap structures, stack variables, or critical control data within the modem processor’s execution environment. In many embedded systems handling telephony functions, these buffers are located in sensitive areas of memory where integrity is paramount for maintaining system stability and security isolation between the baseband processor and application processors.
The operational impact of this vulnerability extends beyond simple denial of service scenarios involving device crashes or reboots. Successful exploitation can lead to arbitrary code execution on the modem firmware or the secure element itself, depending on the architecture's memory protection mechanisms such as NX bit or ASLR effectiveness. If an attacker achieves control over instruction pointers through stack smashing techniques facilitated by this buffer overflow, they may bypass security controls designed to protect subscriber identity and encryption keys. This could allow for sophisticated attacks including location tracking via IMSI catchers that are no longer hindered by standard authentication failures, interception of encrypted communications if session keys can be derived or manipulated, or complete compromise of the device’s telephony stack which often shares resources with general-purpose computing functions in modern smartphones.
Mitigation strategies must focus on both immediate patching and long-term architectural improvements. Vendors should implement strict input validation routines that verify all data lengths against predefined maximums before any memory allocation or copy operations occur during USIM initialization sequences. Utilizing safe string handling libraries and compiler-based protections like stack canaries, address space layout randomization, and control flow integrity will significantly reduce the exploitability of such flaws. Furthermore, adopting formal verification methods for critical protocol handlers in secure elements can help identify these boundary condition errors early in the development lifecycle. Users should ensure their devices are updated with the latest security patches provided by manufacturers, which typically include fixes to the modem firmware or SIM application logic that enforce proper bounds checking during cryptographic key derivation processes.