CVE-2026-20557 in MT2716
Summary
by MITRE • 11/02/2026
In Modem, there is a possible out of bounds write due to a missing bounds check. This could lead to remote escalation of privilege, if a UE has connected to a rogue base station controlled by the attacker, with no additional execution privileges needed. User interaction is not needed for exploitation. Patch ID: MOLY01877236; Issue ID: MSV-9804.
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Analysis
by VulDB Data Team • 11/02/2026
The vulnerability identified under issue identifier MSV-9804 and addressed by patch MOLY01877236 represents a critical security flaw within the modem subsystem of mobile devices, specifically involving an out-of-bounds write condition resulting from insufficient input validation. This type of memory corruption error occurs when the software writes data to a memory location beyond the boundaries of the intended buffer or array structure. In the context of cellular communication protocols, such flaws are particularly dangerous because they reside in low-level components that handle raw network traffic before it is processed by higher-level operating system services. The absence of proper bounds checking allows an attacker who controls the input data to overwrite adjacent memory regions, potentially corrupting critical control structures or overwriting function pointers within the modem firmware.
The operational impact of this vulnerability is severe due to its potential for remote privilege escalation without any user interaction. An adversary can exploit this flaw by establishing a connection with a rogue base station, often referred to as an IMSI catcher or Stingray device in offensive security contexts. By manipulating signaling messages sent during the attachment and authentication procedures between the User Equipment UE and the network infrastructure, the attacker can trigger the out-of-bounds write condition within the modem firmware. Since this process occurs at the radio interface layer, it bypasses many of the standard application-level security controls that protect the main operating system. The exploitation does not require any action from the device user, such as clicking a link or opening an attachment, making it highly effective for automated attacks and persistent compromise scenarios where stealth is required to maintain long-term access.
From a technical classification perspective, this vulnerability aligns with CWE-787 Out-of-bounds Write in the Common Weakness Enumeration taxonomy, which describes situations where data is written past the end of or before the beginning of the intended buffer. Furthermore, the exploitation technique maps directly to MITRE ATT&CK techniques related to Initial Access and Privilege Escalation via cellular network interfaces. Specifically, it relates to tactics involving direct interaction with base stations to execute malicious code or escalate privileges within embedded systems. The lack of execution privilege requirements for the attacker underscores the severity, as even unprivileged processes on the host device cannot prevent this attack vector once the rogue station is active and communicating with the target UE.
Mitigation strategies must focus primarily on applying the vendor-provided patch MOLY01877236 to update the modem firmware and ensure that strict bounds checking mechanisms are implemented in all memory allocation and data handling routines within the cellular stack. Developers should enforce rigorous input validation for all parameters derived from external network sources, ensuring that buffer sizes are verified before any write operations occur. Additionally, implementing runtime protection mechanisms such as Memory Safety features or hardware-enforced isolation between the modem processor and the application processor can limit the blast radius of such vulnerabilities. Network operators and device manufacturers must also prioritize regular security updates to address known weaknesses in protocol implementations, thereby reducing the window of exposure for end-users against sophisticated cellular-based attacks that leverage these low-level memory corruption flaws.