Preface: A modem OTA (Over-the-Air) stack refers to the software and protocol components inside a cellular or wireless modem that handle data and control messages received directly “over the air” from base stations or network operators—most commonly via radio resource control, broadcast channels, or system information blocks (such as SIB1 in 4G/5G networks).
Background: The flaw exists within the Protocol Parsing Engine of the modem stack processing firmware. When the device receives a malicious over-the-air binary packet (such as a manipulated SIB1 scheduling message), the parsing engine extracts the scheduling_length value without proper verification.
Because the code fails to execute an ASN.1 semantic validation check, the invalid length parameter is accepted as legitimate. During memory allocation operations (memset or memcpy), the stack attempts to copy the payload into a fixed 512-byte destination buffer. A malicious payload specifying a length of 768 bytes triggers a stack buffer overflow. This overruns adjacent variables, function return pointers, and critical registers.
Vulnerability details: In the modem OTA stack, there is a possible stack-based buffer overflow due to improper validation of scheduling information in SIB1 messages. This could lead to remote code execution or denial of service with no additional execution privileges needed.
Temporary Mitigations and Workarounds:
As official vendor patches are being deployed by chip manufacturers and mobile network operators, users should adopt the following defensive measures to minimize their attack surface:
• Use Wi-Fi and Enable Airplane Mode: Turn off cellular radios completely when secure Wi-Fi networks are available to close the over-the-air cellular vector.
• Downgrade to LTE-Only Mode: Disable 5G NR capabilities within the device cellular settings to avoid triggering the specific 5G protocol parsing stack.
• Avoid High-Risk Locations: Minimize cell usage near unverified, rogue, or suspicious cellular base stations.
• Apply Carrier Configurations: Promptly accept and install any emergency carrier profile updates distributed by your mobile network operator.
Official announcement: Please refer to the link for details – https://www.tenable.com/cve/CVE-2026-66086