CVE-2021-1955
📋 TL;DR
This vulnerability in Qualcomm Snapdragon chipsets allows denial of service attacks when connections are improperly handled during association rejection in SAP (Service Access Point) cases. It affects a wide range of Qualcomm-powered devices including automotive, mobile, IoT, and wearable products. Attackers can cause system crashes or service disruptions by sending specially crafted connection requests.
💻 Affected Systems
- Snapdragon Auto
- Snapdragon Compute
- Snapdragon Connectivity
- Snapdragon Consumer Electronics Connectivity
- Snapdragon Consumer IOT
- Snapdragon Industrial IOT
- Snapdragon IoT
- Snapdragon Mobile
- Snapdragon Voice & Music
- Snapdragon Wearables
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system crash or persistent denial of service affecting critical functions in automotive, medical, or industrial systems, potentially leading to safety hazards or operational shutdowns.
Likely Case
Temporary service disruption, system instability, or device reboots affecting connectivity and functionality of affected devices.
If Mitigated
Minimal impact with proper network segmentation and updated firmware, though some performance degradation may occur during attack attempts.
🎯 Exploit Status
Exploitation requires network access to vulnerable services and knowledge of specific connection handling flaws. No public exploit code available as of knowledge cutoff.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: July 2021 security updates and later
Vendor Advisory: https://www.qualcomm.com/company/product-security/bulletins/july-2021-bulletin
Restart Required: Yes
Instructions:
1. Check device manufacturer for firmware updates 2. Apply Qualcomm July 2021 or later security patches 3. Update device firmware through manufacturer channels 4. Reboot device after update
🔧 Temporary Workarounds
Network Segmentation
allIsolate vulnerable devices from untrusted networks to prevent remote exploitation
Service Access Control
linuxRestrict access to vulnerable SAP services using firewall rules
iptables -A INPUT -p tcp --dport [vulnerable_port] -j DROP
iptables -A INPUT -p udp --dport [vulnerable_port] -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate vulnerable devices
- Deploy intrusion detection systems to monitor for connection flooding attempts
🔍 How to Verify
Check if Vulnerable:
Check device firmware version against Qualcomm security bulletin. Review system logs for connection rejection errors or service crashes.Check Version:
cat /proc/version | grep -i qualcomm OR check device settings > about phone > kernel versionVerify Fix Applied:
Verify firmware version includes July 2021 or later security patches. Test connection handling under load.📡 Detection & Monitoring
Log Indicators:
- Multiple connection rejections in short time
- SAP service crashes
- System reboots without clear cause
- Kernel panic logs related to connection handling
Network Indicators:
- Unusual connection attempts to SAP ports
- Connection flooding patterns
- Protocol anomalies in association requests
SIEM Query:
source="device_logs" AND ("connection rejected" OR "association failed" OR "SAP crash") | stats count by host