Security researchers from SSD Secure Disclosure have revealed a significant vulnerability affecting Android devices using Unisoc modem firmware. The exploit chain, disclosed in August 2026, leverages a VoLTE video call to gain full access to the Android kernel, impacting devices with Unisoc chipsets such as the Motorola E13, Realme C33, and Xiaomi Redmi A5. Notably, the vulnerability remains unpatched as Unisoc has not responded to outreach attempts by the researchers.
The exploit is a two-stage process that begins with a remote code execution vulnerability disclosed in March 2026. To execute the entire chain, attackers must control a private 4G network and trick victims into accepting a video call. This vulnerability, classified as CWE-1189, involves improper isolation of shared resources on System-on-a-Chip. It affects several Unisoc chipsets, but no CVE identifier is currently assigned.
The researchers demonstrated their findings using open-source tools and specialized equipment to simulate a 4G network environment. Once they gained code execution on the modem, they escalated privileges by altering the modem's ARM Memory Protection Unit settings. This process allowed them to map the entire 32-bit physical address space, including where the Android kernel resides, making it readable, writable, and executable from the modem's perspective.
Despite the gravity of the situation, neither the August 2026 Android Security Bulletin nor any Unisoc advisory address the privilege-escalation flaw. As a result, device owners are left without a patch or mitigation strategy and should remain vigilant for firmware updates from their manufacturers. The vulnerability highlights a broader architectural issue within Unisoc chips, previously documented by Kaspersky ICS CERT. This issue involves shared physical memory between the modem and application processors, which poses a significant security risk.
In 2022, a similar Unisoc modem vulnerability was patched by the company after discovery by Check Point Research. However, the current vulnerabilities disclosed by SSD Secure Disclosure have not yet received such attention, leaving millions of device users exposed.