CVE-2020-25856
📋 TL;DR
A stack buffer overflow vulnerability in Realtek RTL8195A Wi-Fi modules allows remote code execution or denial of service when an attacker impersonates an access point and injects crafted packets during WPA2 handshake. This affects devices using Realtek RTL8195A Wi-Fi modules with firmware versions prior to April 2020. Attackers need knowledge of the network's PSK to exploit this vulnerability.
💻 Affected Systems
- Realtek RTL8195A Wi-Fi Module
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with full device compromise, allowing attacker to install malware, exfiltrate data, or pivot to other network devices.
Likely Case
Denial of service causing Wi-Fi connectivity disruption or device crashes requiring reboot.
If Mitigated
Limited impact if devices are patched or isolated from untrusted networks.
🎯 Exploit Status
Exploitation requires attacker to know the network's PSK and be within Wi-Fi range to impersonate an access point and inject packets during WPA2 handshake.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 2.08 and later (released April 2020)
Vendor Advisory: https://www.realtek.com/en/
Restart Required: Yes
Instructions:
1. Contact device manufacturer for updated firmware. 2. Download firmware version 2.08 or later. 3. Apply firmware update following manufacturer instructions. 4. Reboot device to activate new firmware.
🔧 Temporary Workarounds
Network isolation
allIsolate vulnerable devices on separate network segments to limit attack surface
WPA3 migration
allMigrate to WPA3 networks where supported to prevent WPA2 handshake attacks
🧯 If You Can't Patch
- Disable Wi-Fi and use wired connections only
- Implement strict network segmentation and firewall rules to limit device communication
🔍 How to Verify
Check if Vulnerable:
Check device firmware version via manufacturer's management interface or CLI. If version is below 2.08 and released before April 2020, device is vulnerable.Check Version:
Manufacturer-specific command varies by device. Typically accessed via serial console or management interface.Verify Fix Applied:
Verify firmware version is 2.08 or later after applying update. Test Wi-Fi connectivity and monitor for crashes.📡 Detection & Monitoring
Log Indicators:
- Multiple failed WPA2 handshake attempts
- Unexpected device reboots
- Wi-Fi module crash logs
Network Indicators:
- Unusual WPA2 handshake patterns
- Spoofed access point beacons
- Malformed 802.11 packets
SIEM Query:
source="wifi_logs" AND (event="handshake_failure" OR event="buffer_overflow")