CVE-2025-27034: Qualcomm Fastconnect Use-After-Free Flaw

CVE-2025-27034 Overview

CVE-2025-27034 is a critical memory corruption vulnerability affecting a wide range of Qualcomm chipsets and firmware. The vulnerability occurs during the processing of the Public Land Mobile Network (PLMN) selection from a Steering of Roaming (SOR) failed list. Due to improper validation of array indices (CWE-129), an attacker could exploit this flaw to corrupt memory, potentially leading to remote code execution, system instability, or complete device compromise.

This vulnerability impacts numerous Qualcomm Snapdragon mobile platforms, 5G modem-RF systems, FastConnect Wi-Fi/Bluetooth solutions, and various IoT and automotive components. Given the widespread deployment of these chipsets in smartphones, tablets, laptops, automotive systems, and IoT devices, the potential attack surface is extensive.

Critical Impact

Remote attackers can exploit this memory corruption vulnerability over the network without authentication or user interaction, potentially achieving complete device compromise including confidentiality, integrity, and availability impacts.

Affected Products

• Qualcomm Snapdragon 8 Gen 1/2/3 Mobile Platforms and Firmware
• Qualcomm Snapdragon X55/X62/X65/X70/X72/X75 5G Modem-RF Systems
• Qualcomm FastConnect 6200/6700/6800/6900/7800 Firmware
• Qualcomm Snapdragon 865/870/888 5G Mobile Platforms
• Qualcomm 315 5G IoT Modem and Firmware
• Qualcomm Snapdragon Auto 5G Modem-RF Gen 1/2

Discovery Timeline

• September 24, 2025 - CVE-2025-27034 published to NVD
• November 28, 2025 - Last updated in NVD database

Technical Details for CVE-2025-27034

Vulnerability Analysis

This memory corruption vulnerability stems from improper validation of array indices when processing PLMN entries from a SOR (Steering of Roaming) failed list. The SOR mechanism is used in cellular networks to manage roaming preferences and restrictions. When a device encounters a failed PLMN list, it must properly validate and process each entry before selecting an appropriate network.

The flaw allows attackers to trigger out-of-bounds memory access by supplying malformed or specially crafted PLMN data. Since this vulnerability can be exploited remotely over the network without requiring any privileges or user interaction, it presents a significant risk to mobile devices and connected systems. Successful exploitation could allow an attacker to execute arbitrary code with elevated privileges, potentially gaining full control of the affected device's modem subsystem.

Root Cause

The vulnerability is classified under CWE-129 (Improper Validation of Array Index). The modem firmware fails to properly validate array indices when iterating through or accessing elements in the SOR failed PLMN list. This allows an attacker-controlled index to reference memory locations outside the bounds of the intended array, leading to memory corruption.

When processing network signaling messages containing PLMN selection data, the firmware does not adequately verify that index values fall within expected boundaries. This oversight enables exploitation through crafted cellular network messages or malicious base station emulation.

Attack Vector

The vulnerability is exploitable over the network (cellular/wireless) without requiring authentication or user interaction. An attacker could potentially exploit this vulnerability through:

The attack can be initiated by a malicious or compromised cellular base station sending specially crafted network signaling messages containing malformed PLMN data. The attacker would craft a message with an invalid array index that causes the modem firmware to access or write memory outside the intended buffer boundaries. This could overwrite critical data structures, function pointers, or return addresses, ultimately leading to arbitrary code execution within the modem context.

Given that no proof-of-concept exploit code has been publicly released and this vulnerability is not currently known to be exploited in the wild, organizations should prioritize patching while maintaining appropriate monitoring.

Detection Methods for CVE-2025-27034

Indicators of Compromise

• Unexpected modem crashes, restarts, or connectivity disruptions on affected devices
• Anomalous cellular network behavior including repeated connection attempts to unknown PLMNs
• Unusual memory consumption or access patterns in modem-related system logs
• Signs of baseband exploitation such as unauthorized network registrations or data exfiltration

Detection Strategies

• Monitor device firmware versions against the Qualcomm September 2025 Security Bulletin affected product list
• Implement network-level monitoring for anomalous cellular signaling patterns at the carrier level
• Deploy endpoint detection solutions capable of monitoring modem subsystem behavior and memory anomalies
• Audit mobile device management (MDM) systems for devices running vulnerable firmware versions

Monitoring Recommendations

• Enable detailed logging for cellular connectivity events and PLMN selection activities where supported
• Configure alerting for devices experiencing repeated modem crashes or unexpected restarts
• Establish baseline behavior for modem subsystem activity to detect deviations indicating potential exploitation
• Coordinate with mobile carriers for visibility into suspicious base station activity in enterprise environments

How to Mitigate CVE-2025-27034

Immediate Actions Required

• Identify all devices in your environment using affected Qualcomm chipsets and firmware versions
• Apply firmware updates from device manufacturers that incorporate the Qualcomm security patches
• Prioritize patching for high-value targets and devices with access to sensitive networks or data
• Consider network segmentation to limit the blast radius of potential modem-level compromise

Patch Information

Qualcomm has addressed this vulnerability in the September 2025 Security Bulletin. Organizations should obtain and apply firmware updates through their device manufacturers (OEMs) such as Samsung, Google, OnePlus, Xiaomi, and others who incorporate Qualcomm chipsets. The specific patch availability depends on individual OEM release schedules.

For detailed patch information and affected product versions, refer to the Qualcomm Security Bulletin September 2025.

Workarounds

• No complete workarounds are available; firmware patching is the definitive remediation
• Implement strict MDM policies to enforce rapid firmware updates on managed devices
• Where possible, use enterprise network connectivity (Wi-Fi) instead of cellular for sensitive operations until patches are applied
• Consider deploying cellular intrusion detection systems (IDS) in high-security environments to detect potential exploitation attempts

# Example: Check Android device firmware version for affected chipsets
# Run via ADB (Android Debug Bridge)
adb shell getprop ro.board.platform
adb shell getprop ro.build.fingerprint
adb shell getprop gsm.version.baseband