CVE-2021-1975
📋 TL;DR
CVE-2021-1975 is a critical heap overflow vulnerability in Qualcomm Snapdragon chipsets that allows remote code execution via malformed DNS responses. Attackers can exploit this to execute arbitrary code with kernel privileges on affected devices. This affects numerous Qualcomm Snapdragon platforms across automotive, compute, IoT, wearables, and other embedded systems.
💻 Affected Systems
- Snapdragon Auto
- Snapdragon Compute
- Snapdragon Connectivity
- Snapdragon Consumer IOT
- Snapdragon Industrial IOT
- Snapdragon IoT
- Snapdragon Voice & Music
- Snapdragon Wearables
📦 What is this software?
Sd7c Firmware by Qualcomm
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing remote attackers to execute arbitrary code with kernel privileges, potentially leading to persistent backdoors, data theft, or device bricking.
Likely Case
Remote code execution leading to device compromise, data exfiltration, or integration into botnets for DDoS attacks.
If Mitigated
Limited impact if devices are behind firewalls with DNS filtering and have network segmentation preventing direct internet access.
🎯 Exploit Status
Exploitation requires sending specially crafted DNS responses, but no authentication is needed. The vulnerability is in parsing logic, making reliable exploitation feasible for skilled attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Varies by device manufacturer - check with OEM for specific firmware updates
Vendor Advisory: https://www.qualcomm.com/company/product-security/bulletins/november-2021-bulletin
Restart Required: Yes
Instructions:
1. Contact device manufacturer for firmware updates. 2. Apply Qualcomm-provided patches through OEM firmware updates. 3. Reboot device after update. 4. Verify patch installation through version checks.
🔧 Temporary Workarounds
DNS Response Filtering
allDeploy DNS filtering solutions to block malformed DNS responses before they reach vulnerable devices.
Network Segmentation
allIsolate affected devices in separate network segments with restricted DNS access.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate vulnerable devices from untrusted networks
- Deploy DNS filtering appliances that can detect and block malformed DNS packets
🔍 How to Verify
Check if Vulnerable:
Check device firmware version against manufacturer's security bulletins. Use 'getprop ro.build.fingerprint' on Android devices or check firmware version in device settings.Check Version:
Android: 'getprop ro.build.version.security_patch' and 'getprop ro.build.fingerprint'. Linux-based: Check firmware version via manufacturer-specific commands.Verify Fix Applied:
Verify firmware version has been updated to a version listed as patched by the device manufacturer. Check for security patch level dated after November 2021.📡 Detection & Monitoring
Log Indicators:
- DNS parsing errors in system logs
- Unexpected process crashes in network stack
- Memory corruption warnings in kernel logs
Network Indicators:
- Unusual DNS response patterns
- DNS packets with malformed domain names
- Traffic to devices from unexpected DNS servers
SIEM Query:
source="dns" AND (message="*heap*" OR message="*overflow*" OR message="*corruption*") OR source="kernel" AND message="*panic*" AND process="*dns*"