CVE-2026-20503 in MT2716
Summary
by MITRE • 09/07/2026
In Modem, there is a possible system crash due to a missing bounds check. This could lead to remote denial of service, 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: MOLY01371002; Issue ID: MSV-9020.
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Analysis
by VulDB Data Team • 09/07/2026
The vulnerability described involves a critical flaw within the modem firmware of mobile devices, specifically characterized by a missing bounds check that can result in a system crash. This type of error typically occurs when software processes input data without verifying whether the length or index of that data falls within acceptable limits defined by the application's memory allocation. In the context of cellular modems, this often pertains to how protocol stack layers handle signaling messages received from the network infrastructure. When an attacker controls a rogue base station, they can craft maliciously formatted packets containing oversized fields or invalid indices. Upon receiving these packets, the modem firmware fails to validate the boundaries before processing them, leading to memory corruption such as buffer overflows or out-of-bounds reads and writes. This unchecked access corrupts critical data structures within the modem's operating environment, ultimately causing a fatal exception that forces the system to reboot or become unresponsive.
From an operational impact perspective, this vulnerability enables a remote denial of service attack against connected user equipment without requiring any prior authentication or elevated privileges on the device itself. The attacker does not need physical access to the target phone nor do they need to trick the user into installing malicious software. Instead, exploitation relies solely on the victim's device connecting to a compromised cellular tower under the attacker's control. This scenario is particularly dangerous in urban environments where attackers can deploy portable base stations or exploit vulnerabilities in network infrastructure to impersonate legitimate cell towers. The resulting denial of service disrupts all voice and data services for the affected user, effectively rendering their mobile device useless until it is manually restarted or reconnected to a trusted network.
This vulnerability aligns with Common Weakness Enumeration (CWE) standards, specifically CWE-125: Out-of-bounds Read and CWE-787: Out-of-bounds Write, depending on the specific nature of the memory corruption triggered by the missing bounds check. In terms of offensive security frameworks, this attack vector corresponds to MITRE ATT&CK techniques related to network manipulation and denial of service via compromised infrastructure components. The ability to exploit a modem-level flaw through radio interface interactions highlights the risks associated with trusting external signals without rigorous validation at the lowest levels of the protocol stack. Such flaws undermine the integrity of the communication channel between the user equipment and the cellular core network, allowing an adversary to disrupt availability services remotely.
Mitigation strategies for this vulnerability primarily involve applying the vendor-provided firmware patch identified as MOLY01371002 associated with issue ID MSV-9020. Device manufacturers must ensure that their modem software includes robust input validation mechanisms across all protocol layers, particularly in areas handling radio resource control and mobility management messages. Developers should implement strict bounds checking for all array accesses and buffer operations to prevent out-of-bounds memory access. Additionally, integrating fuzzing techniques during the development lifecycle can help identify similar logic errors before deployment. For end-users, keeping device firmware up to date is essential to mitigate this risk. Network operators may also consider implementing signaling message validation at the base station level to filter out malformed packets from rogue sources, although software patches on the user equipment remain the most direct defense against exploitation via compromised infrastructure.