CVE-2026-20504 in MT2735
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: MOLY00755024; Issue ID: MSV-7865.
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Analysis
by VulDB Data Team • 09/07/2026
The vulnerability described involves a critical flaw within the modem subsystem 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 structures. In the context of cellular modems, which handle complex signaling protocols and continuous streams of network data, such an oversight allows malformed packets to corrupt internal buffers or trigger illegal memory access operations. The absence of proper validation means that any unexpected input size can overwrite adjacent memory regions, leading to stack corruption, heap overflow conditions, or general protection faults that force the operating system to terminate the affected process or reboot the entire device to maintain stability.
The operational impact of this vulnerability is severe due to its potential for remote exploitation without user interaction. An attacker who controls a rogue base station can craft specific malicious signaling messages designed to trigger the missing bounds check within the modem firmware. When a User Equipment (UE) connects to this compromised infrastructure, it automatically processes these signals as part of standard network registration or data transmission procedures. Because no additional execution privileges are required on the device itself and no user action such as clicking a link is necessary, the attack vector is highly efficient and difficult for end-users to prevent through behavioral changes alone. The primary consequence is a remote denial of service condition where the mobile device becomes unresponsive, crashes repeatedly, or loses connectivity entirely, effectively disrupting communication services for the victim until the device is restarted or patched.
From a security classification perspective, this flaw aligns with CWE-125 Out-of-bounds Read and CWE-787 Out-of-bounds Write depending on whether the missing check leads to reading sensitive memory data or writing corrupt data that crashes the system. The exploitation technique falls under MITRE ATT&CK techniques related to Denial of Service, specifically leveraging infrastructure components like cellular networks rather than traditional internet-based vectors. This highlights a growing concern in mobile security where the physical layer and radio resource control layers are increasingly targeted by sophisticated adversaries capable of deploying portable or fixed rogue base stations known as IMSI catchers or stingrays that can be repurposed for malicious signaling attacks beyond mere surveillance.
Mitigation strategies must focus on both immediate patching and long-term architectural improvements. The primary remediation is the application of the provided patch, identified by MOLY00755024 which addresses issue MSV-7865 in the modem firmware. This update likely introduces rigorous input validation routines that verify packet lengths against buffer capacities before processing begins. Beyond software updates, device manufacturers should implement stricter isolation between the baseband processor and application processors to limit the blast radius of such crashes. Network operators can also assist by deploying detection systems capable of identifying anomalous signaling patterns indicative of rogue base station activity or malformed protocol messages, thereby alerting users to potential threats in their vicinity and reducing exposure time until patches are deployed across the device fleet.