CVE-2025-21477 Overview
CVE-2025-21477 is an Improper Input Validation vulnerability (CWE-20) affecting a wide range of Qualcomm chipsets and firmware. The vulnerability occurs during the processing of Common Control Channel (CCCH) data when a network sends data with an invalid length, resulting in a transient Denial of Service (DoS) condition. This affects multiple Qualcomm Snapdragon mobile platforms, 5G modems, FastConnect connectivity components, and associated firmware across IoT, automotive, and mobile device ecosystems.
Critical Impact
Attackers can remotely trigger a transient Denial of Service condition on affected Qualcomm-powered devices by sending malformed CCCH network data with invalid length parameters, potentially disrupting cellular connectivity for smartphones, IoT devices, and automotive systems.
Affected Products
- Qualcomm Snapdragon 8 Gen 1/2/3 Mobile Platforms and firmware
- Qualcomm Snapdragon 865/870/888 5G Mobile Platforms and firmware
- Qualcomm Snapdragon X55/X62/X65/X70/X72/X75 5G Modem-RF Systems and firmware
- Qualcomm FastConnect 6200/6700/6800/6900/7800 and firmware
- Qualcomm 315 5G IoT Modem and firmware
- Qualcomm Snapdragon Auto 5G Modem-RF Gen 1/2 and firmware
Discovery Timeline
- August 6, 2025 - CVE-2025-21477 published to NVD
- August 20, 2025 - Last updated in NVD database
Technical Details for CVE-2025-21477
Vulnerability Analysis
This vulnerability stems from improper input validation in the CCCH (Common Control Channel) data processing routines within affected Qualcomm modem firmware. The CCCH is a critical logical channel in cellular networks used for control signaling between the mobile device and the base station. When the network transmits CCCH data containing an invalid or unexpected length field, the vulnerable firmware fails to properly validate this input before processing.
The lack of adequate boundary checking on incoming length parameters allows an attacker with network-level access to craft malicious CCCH messages that trigger a transient DoS condition. This causes the modem to temporarily become unresponsive or reset, disrupting cellular connectivity on the affected device. The attack can be executed remotely over the air interface without requiring any user interaction or local access to the device.
Root Cause
The root cause is classified as CWE-20 (Improper Input Validation). The affected Qualcomm firmware components do not adequately validate the length field in incoming CCCH data packets before processing them. When an invalid length value is received—such as a length exceeding expected bounds or mismatched with actual payload size—the processing routine fails to handle this condition gracefully, leading to a transient denial of service.
Attack Vector
The attack vector is network-based, requiring no authentication, privileges, or user interaction. An attacker operating a rogue base station or with the ability to inject malicious signaling messages into cellular network traffic could exploit this vulnerability. The attack specifically targets the modem's CCCH processing functionality by transmitting specially crafted control channel messages with invalid length parameters.
The attack flow involves:
- Attacker establishes a rogue cell or gains position to inject network signaling
- Malformed CCCH data with invalid length is transmitted to target device
- Vulnerable modem firmware processes the malformed data without proper validation
- Processing failure causes transient DoS, temporarily disrupting connectivity
The transient nature of this DoS means that while device connectivity is disrupted, the device typically recovers after the modem resets or re-establishes connection. However, repeated exploitation could cause persistent connectivity issues.
Detection Methods for CVE-2025-21477
Indicators of Compromise
- Unexpected modem resets or connectivity drops on Qualcomm-powered devices
- Unusual patterns of cellular network disconnections and reconnections
- Modem crash logs indicating CCCH processing failures
- Anomalous control channel signaling detected at network infrastructure level
Detection Strategies
- Monitor modem diagnostics and crash logs for CCCH-related processing errors
- Implement network-side monitoring for anomalous control channel message patterns
- Deploy endpoint detection solutions capable of monitoring modem subsystem health
- Analyze baseband firmware logs for unexpected length validation failures
Monitoring Recommendations
- Enable detailed modem logging on critical Qualcomm-powered devices in enterprise fleets
- Configure network infrastructure to detect potential rogue base station activity
- Implement SentinelOne Singularity Platform for comprehensive endpoint visibility and anomaly detection on mobile and IoT devices
- Monitor for patterns of transient connectivity issues across device populations that may indicate targeted exploitation
How to Mitigate CVE-2025-21477
Immediate Actions Required
- Review the Qualcomm Security Bulletin August 2025 for complete affected product list
- Contact device manufacturers for firmware update availability and timelines
- Prioritize patching for devices in high-security environments or critical infrastructure
- Inventory all Qualcomm-powered devices in your environment to assess exposure
Patch Information
Qualcomm has disclosed this vulnerability in their August 2025 Security Bulletin. Organizations should obtain firmware updates through their device manufacturers (OEMs), as Qualcomm provides patches to OEMs who then distribute updates to end users. The specific patch implementation will vary by device manufacturer and platform.
For detailed information on affected chipsets and patch availability, consult the Qualcomm Security Bulletin August 2025.
Workarounds
- No direct workarounds are available as the vulnerability resides in modem firmware
- Minimize exposure by avoiding connections to untrusted or public cellular networks where rogue base stations may operate
- Consider enabling Airplane Mode when in high-risk environments until patches are applied
- For critical deployments, evaluate network-based protections that can detect and filter anomalous signaling
# Check device firmware version (Android example)
adb shell getprop ro.build.fingerprint
adb shell getprop ro.baseband
# Monitor for modem crashes on Android
adb logcat -b radio | grep -i "crash\|reset\|ccch"
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
