CVE-2026-20594 in Modem
Summary
by MITRE • 11/02/2026
In Modem, there is a possible out of bounds read 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: MOLY01349680 / MOLY01369097; Issue ID: MSV-9364.
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Analysis
by VulDB Data Team • 11/02/2026
The vulnerability identified in the modem firmware, associated with patch identifiers MOLY01349680 and MOLY01369097 under issue reference MSV-9364, represents a critical security flaw rooted in improper input validation within the cellular protocol stack. Specifically, this is an out-of-bounds read condition caused by a missing bounds check during the processing of signaling messages or data structures received from the network side. In modern mobile communication systems, such as LTE and 5G NR, modems continuously process complex control plane messages to manage connection states, handovers, and security contexts. When these messages are parsed, specific fields must be validated against expected limits to ensure that subsequent memory operations remain within allocated buffers. The absence of this validation allows an attacker who controls the radio interface to supply crafted inputs that exceed the designated buffer boundaries, triggering a read operation outside the intended memory region.
This technical flaw is classified under CWE-125, which denotes Out-of-bounds Read vulnerabilities. From a tactical perspective, this vulnerability aligns with MITRE ATT&CK techniques related to Denial of Service against network infrastructure or endpoints, particularly those involving exploitation via radio interface manipulation. The primary operational impact of this weakness is remote denial of service. Because the modem processes these messages autonomously without requiring user interaction, an attacker can exploit the flaw simply by having a User Equipment connect to a rogue base station that they control. This scenario typically involves setting up a fake cell tower or using specialized radio equipment to broadcast malicious signaling packets directly to the target device's modem firmware.
The exploitation chain does not require any execution privileges on the victim device, nor does it depend on user actions such as clicking links or opening files. The vulnerability is triggered passively during normal network attachment procedures or when the UE receives specific configuration updates from the rogue base station. By sending malformed packets that cause an out-of-bounds read, the attacker can corrupt memory state information within the modem's processing unit. This corruption often leads to a crash of the modem firmware, resulting in a loss of cellular connectivity for the device. In severe cases, depending on how the operating system handles the fault, it may lead to broader system instability or require a reboot of the mobile device to restore service.
Mitigation strategies primarily rely on the implementation of the provided patches MOLY01349680 and MOLY01369097, which introduce rigorous bounds checking logic into the modem's protocol stack parsers. These updates ensure that all incoming data fields are validated against their expected maximum lengths before being processed or copied into memory buffers. For end-users, applying these firmware updates is essential to close this attack vector. Additionally, network operators and device manufacturers should consider implementing deeper packet inspection mechanisms at the core network level where feasible, although direct radio interface attacks remain difficult to mitigate without endpoint-level fixes. Security awareness regarding rogue base stations remains relevant, as users in high-risk areas might benefit from disabling automatic network selection or using devices with robust modem security features that include memory protection techniques such as Address Space Layout Randomization and stack canaries, which can further hinder exploitation even if the initial bounds check is bypassed.