Executive Summary

CVE-2025-53913 is an excessive privileges vulnerability in Calix GigaCenter ONT devices using Quantenna SoC modules. It allows an attacker with physical access to gain unauthenticated root access via the UART debugging interface connected to the Quantenna SoC. The UART console does not require credentials, so by physically disassembling the device and connecting to the UART interface, an attacker can obtain full root shell access without authentication. [1]

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Impact Analysis

An attacker exploiting this vulnerability can gain full root control of the affected device. This allows them to view sensitive information such as user accounts, configuration files, firmware, and web application code. They can also create backdoors, modify or enable system services, and make persistent firmware changes, potentially compromising the security and integrity of the device and network. [1]

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Detection Guidance

This vulnerability cannot be detected remotely on the network as it requires physical access to the device's UART debugging interface. Detection involves physically disassembling the router to locate the UART interfaces on the PCB, specifically the Quantenna SoC UART interface. Connecting via a USB-to-UART adapter at 115200 baud rate to this interface grants root shell access without authentication. There are no specific network commands to detect this vulnerability remotely. [1]

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Mitigation Strategies

To mitigate this vulnerability, apply the R12.2.13.4 patch provided by Calix. This patch is only available to authorized users, so end users should contact their broadband service providers to ensure the update is applied. Since the vulnerability requires physical access, restricting physical access to the device and securing the device location can also help reduce risk. [1]

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