Stack Buffer Overflow in Sierra Wireless HL7800 Modem Driver

CVE-2026-12520

What is CVE-2026-12520?

The Sierra Wireless HL7800 modem driver is prone to a stack buffer overflow vulnerability due to improper handling of AT responses. The issue arises within the driver's structure that uses a 128-byte stack buffer but fails to adequately control input sizes. When the modem emits overly long responses, particularly from the +KCELLMEAS command, it can lead to either writing past the buffer's boundary or even potential code execution in kernel context, making it particularly severe. The corruption occurs in the RX thread of the kernel, exposing systems to crashes and security breaches. A patch has been introduced to enforce boundaries in response handling, but risks remain for devices that do not implement this fix.

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