CVE-2025-20738
📋 TL;DR
This CVE describes an out-of-bounds write vulnerability in MediaTek's wlan AP driver due to incorrect bounds checking. It allows local privilege escalation from System to higher privileges without user interaction. Affects devices using MediaTek wireless chipsets with vulnerable driver versions.
💻 Affected Systems
- MediaTek wireless chipsets with wlan AP driver
📦 What is this software?
Openwrt by Openwrt
Openwrt by Openwrt
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with kernel-level code execution, allowing attackers to install persistent malware, steal sensitive data, or disable security controls.
Likely Case
Local privilege escalation enabling attackers to bypass application sandboxes, access protected system resources, or install malicious drivers.
If Mitigated
Limited impact if proper kernel hardening, driver signing enforcement, and privilege separation are implemented.
🎯 Exploit Status
Exploitation requires System privilege first, then uses driver vulnerability for escalation. No public exploit available at disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: WCNCR00435342
Vendor Advisory: https://corp.mediatek.com/product-security-bulletin/November-2025
Restart Required: Yes
Instructions:
1. Check device uses MediaTek wireless hardware. 2. Contact device manufacturer for firmware update containing patch WCNCR00435342. 3. Apply firmware update. 4. Reboot device to load patched driver.
🔧 Temporary Workarounds
Disable vulnerable driver module
linuxPrevent loading of vulnerable wlan AP driver module
echo 'blacklist mtk_wlan_ap' >> /etc/modprobe.d/blacklist.conf
rmmod mtk_wlan_ap
Restrict driver loading permissions
linuxSet strict permissions on driver module file
chmod 600 /lib/modules/$(uname -r)/kernel/drivers/net/wireless/mediatek/mtk_wlan_ap.ko
🧯 If You Can't Patch
- Implement strict privilege separation to limit System account access
- Deploy kernel hardening measures like SELinux/AppArmor with strict policies
🔍 How to Verify
Check if Vulnerable:
Check driver version: lsmod | grep mtk_wlan_ap and modinfo mtk_wlan_ap | grep versionCheck Version:
modinfo mtk_wlan_ap | grep -i versionVerify Fix Applied:
Verify patch applied: dmesg | grep WCNCR00435342 or check driver version matches patched release📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing driver loading errors
- System logs with privilege escalation attempts
- Driver module loading from unusual paths
Network Indicators:
- Unusual wireless driver activity patterns
- Driver communication with unexpected endpoints
SIEM Query:
source="kernel" AND "mtk_wlan_ap" AND ("out of bounds" OR "privilege escalation")