CVE-2026-20556 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: MOLY01876662; Issue ID: MSV-9833.
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Analysis
by VulDB Data Team • 11/02/2026
The vulnerability identified under issue identifier MSV-9833 and addressed by patch MOLY01876662 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 stacks, such flaws are particularly dangerous because they reside in low-level components that handle critical signaling protocols and radio resource control messages. The absence of proper bounds checking allows an attacker who controls the input stream from the network side to overwrite adjacent memory regions with arbitrary data, potentially corrupting stack frames, heap metadata, or function return addresses.
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 between the target device and a rogue base station under their control. By transmitting specially crafted signaling messages that trigger the vulnerable code path within the modem firmware, the attacker can induce the out-of-bounds write condition. Since the modem often operates with elevated privileges to manage hardware resources and network connections successfully exploiting this flaw allows an attacker to gain unauthorized access to sensitive system areas or execute arbitrary code at a high privilege level. This effectively bypasses standard security controls that rely on user consent or application-level isolation, as the exploitation occurs deep within the communication stack before higher-level operating system protections can intervene.
From a threat modeling perspective, this vulnerability aligns with CWE-787: Out-of-bounds Write, which is categorized under CWE-120: Buffer Copy without Checking Size of Input. The attack vector corresponds to ATT&CK technique T1563.002: Remote Service Exploitation via Cellular Network Interfaces, specifically leveraging the lack of authentication and integrity verification in certain legacy or poorly configured cellular protocols such as GSM or LTE signaling layers. The ability to escalate privileges remotely through a physical layer connection highlights the risks associated with trusting network-originated data without rigorous validation. This scenario underscores the importance of secure coding practices within embedded systems that handle external inputs, particularly those originating from untrusted networks like public radio access networks.
Mitigation strategies for this vulnerability primarily involve the implementation of strict input validation and bounds checking mechanisms within the modem firmware codebase. Developers must ensure that all buffer operations verify that destination indices remain within allocated memory limits before performing write operations. Additionally, employing compiler-based security features such as stack canaries, address space layout randomization, and data execution prevention can help mitigate the impact of successful exploitation attempts by making it more difficult for attackers to achieve reliable code execution or bypass memory protection mechanisms. Regular firmware updates provided through patches like MOLY01876662 are essential to remediate these flaws at the source. Furthermore, network operators should consider implementing signaling firewalls and anomaly detection systems that can identify and block malformed packets originating from rogue base stations, thereby reducing the attack surface available to adversaries attempting to exploit cellular protocol vulnerabilities.