CVE-2025-21488: Qualcomm Fastconnect Info Disclosure Flaw

CVE-2025-21488 Overview

CVE-2025-21488 is an information disclosure vulnerability affecting Qualcomm chipset firmware that occurs during the decoding of Real-time Transport Protocol (RTP) packet headers received by the User Equipment (UE) from the network. The vulnerability is triggered when the padding bit is set in maliciously crafted RTP packets, leading to potential exposure of sensitive memory contents.

This vulnerability affects a broad range of Qualcomm products including Snapdragon mobile platforms, FastConnect connectivity modules, automotive platforms, wearables, and various wireless connectivity chipsets. The widespread deployment of affected Qualcomm components across mobile devices, IoT systems, and automotive applications makes this a significant security concern.

Critical Impact

Network-based attackers can exploit improper RTP packet header parsing to leak sensitive information from affected devices without requiring authentication or user interaction.

Affected Products

• Qualcomm Snapdragon 8 Gen 1/2/3 Mobile Platforms
• Qualcomm FastConnect 6200/6700/6900/7800 Firmware
• Qualcomm Snapdragon 820 Automotive Platform
• Qualcomm Snapdragon XR1/XR2 5G Platforms
• Qualcomm WCN Series Wireless Connectivity Chips (WCN3620-WCN7881)
• Qualcomm SA6145P/SA6155/SA8155 Automotive Platforms

Discovery Timeline

• September 24, 2025 - CVE-2025-21488 published to NVD
• November 28, 2025 - Last updated in NVD database

Technical Details for CVE-2025-21488

Vulnerability Analysis

This vulnerability is classified under CWE-126 (Buffer Over-read), indicating that the firmware improperly reads beyond the bounds of allocated memory buffers when processing RTP packet headers. The flaw resides in the RTP header decoding logic, specifically in how the firmware handles packets with the padding bit enabled.

When an RTP packet arrives with the padding flag set, the decoding routine fails to properly validate buffer boundaries before reading header fields. This allows an attacker to craft RTP packets that trigger out-of-bounds read operations, potentially exposing adjacent memory contents that may contain sensitive data such as encryption keys, authentication tokens, or other privileged information.

The vulnerability can be exploited remotely over the network without requiring any authentication or user interaction, making it particularly dangerous for devices exposed to untrusted network traffic. The impact is primarily confidentiality-focused, with potential for limited availability impact as malformed packets may cause processing errors.

Root Cause

The root cause is a buffer over-read condition (CWE-126) in the RTP packet header parsing code within Qualcomm chipset firmware. When processing incoming RTP packets from the network, the firmware's decoding routine does not properly validate the relationship between the padding indicator bit, the actual packet length, and the buffer boundaries before reading header data. This allows crafted packets to cause reads beyond the intended buffer, leaking memory contents to the attacker.

Attack Vector

The attack vector for CVE-2025-21488 is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by:

1. Sending specially crafted RTP packets to a vulnerable device over the network
2. Setting the padding bit in the RTP header while manipulating packet length fields
3. Causing the firmware to perform out-of-bounds memory reads during packet processing
4. Extracting leaked memory contents from the device's responses or timing behavior

The attack is particularly concerning in scenarios involving VoIP calls, video conferencing, or any real-time media streaming where RTP is used for transport.

The vulnerability manifests in the RTP packet header decoding routine when handling the padding bit field. When an RTP packet arrives with the padding flag enabled, the firmware attempts to read the padding length from the last octet of the payload without first validating that the packet length is sufficient. This can cause the decoder to read beyond the allocated buffer boundaries, exposing adjacent memory contents.

For detailed technical analysis, refer to the Qualcomm Security Bulletin September 2025.

Detection Methods for CVE-2025-21488

Indicators of Compromise

• Anomalous RTP traffic patterns with unusual padding bit configurations targeting mobile or IoT devices
• Unexpected network behavior or data exfiltration from devices running affected Qualcomm chipsets
• Memory access violations or crashes in RTP processing components logged in device diagnostics
• Network captures showing malformed RTP packets with inconsistent length and padding fields

Detection Strategies

• Deploy network intrusion detection rules to identify RTP packets with suspicious padding configurations or malformed headers
• Monitor for unusual RTP traffic volumes or patterns targeting devices with Qualcomm chipsets
• Implement deep packet inspection for RTP protocol anomalies at network perimeter
• Enable firmware-level logging on affected devices to capture RTP processing errors

Monitoring Recommendations

• Establish baseline RTP traffic patterns and alert on deviations that may indicate exploitation attempts
• Monitor device telemetry for unexpected crashes or restarts in media processing components
• Track firmware versions across device fleet to identify unpatched systems
• Implement network segmentation to limit exposure of vulnerable devices to untrusted traffic

How to Mitigate CVE-2025-21488

Immediate Actions Required

• Review device inventory to identify all systems using affected Qualcomm chipsets and firmware
• Apply firmware updates from device manufacturers as they become available incorporating Qualcomm patches
• Implement network-level filtering to block or inspect suspicious RTP traffic from untrusted sources
• Consider network segmentation to isolate vulnerable devices until patches can be applied

Patch Information

Qualcomm has addressed this vulnerability in their September 2025 security bulletin. Organizations should obtain updated firmware from their device manufacturers (OEMs) who integrate Qualcomm chipsets. The patch addresses the buffer over-read condition by implementing proper bounds checking in the RTP packet header decoding routine before processing packets with the padding bit set.

Refer to the Qualcomm Security Bulletin September 2025 for detailed patch information and affected product lists.

Workarounds

• Deploy network-level controls such as firewalls or IPS to filter potentially malicious RTP traffic
• Limit exposure of affected devices to untrusted networks where possible
• Consider disabling or restricting real-time media features on critical systems until patches are applied
• Implement network monitoring to detect and respond to exploitation attempts

# Example: Network filtering for suspicious RTP traffic on Linux gateway
# Block RTP packets from untrusted sources (adjust ports and IPs as needed)
iptables -A INPUT -p udp --dport 5004:5005 -s untrusted_network/24 -j DROP
iptables -A INPUT -p udp --dport 16384:32767 -s untrusted_network/24 -j LOG --log-prefix "RTP_BLOCKED: "