CVE-2025-20739
📋 TL;DR
This vulnerability in MediaTek wlan AP driver allows an attacker with System privilege to perform an out-of-bounds write, potentially leading to local privilege escalation. The flaw requires no user interaction for exploitation. Systems using affected MediaTek wireless components are at risk.
💻 Affected Systems
- MediaTek wlan AP driver
📦 What is this software?
Openwrt by Openwrt
Openwrt by Openwrt
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through local privilege escalation to kernel-level access, enabling arbitrary code execution, persistence, and data exfiltration.
Likely Case
Local attackers with initial System access escalate privileges to gain deeper system control, potentially installing malware or accessing sensitive data.
If Mitigated
With proper privilege separation and kernel hardening, impact is limited to denial of service or controlled privilege escalation within security boundaries.
🎯 Exploit Status
Exploitation requires System privilege initially and knowledge of driver internals. No public exploit available as of advisory date.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply patch ID: WCNCR00435340
Vendor Advisory: https://corp.mediatek.com/product-security-bulletin/November-2025
Restart Required: Yes
Instructions:
1. Download patch WCNCR00435340 from MediaTek. 2. Apply to affected driver source code. 3. Recompile kernel/driver module. 4. Reboot system to load patched driver.
🔧 Temporary Workarounds
Disable vulnerable driver module
linuxUnload or blacklist the affected wlan AP driver module to prevent exploitation
rmmod mtk_wlan_ap
echo 'blacklist mtk_wlan_ap' >> /etc/modprobe.d/blacklist.conf
Restrict System privilege access
linuxImplement strict access controls to limit accounts with System privilege
usermod -aG sudo username
visudo to edit sudoers file
🧯 If You Can't Patch
- Implement strict privilege separation and least privilege principles
- Monitor for unusual privilege escalation attempts and kernel module loading
🔍 How to Verify
Check if Vulnerable:
Check if MediaTek wlan AP driver is loaded: lsmod | grep mtk_wlan_apCheck Version:
modinfo mtk_wlan_ap | grep versionVerify Fix Applied:
Verify patch WCNCR00435340 is applied in driver version and no out-of-bounds write occurs in testing📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing driver crashes or out-of-bounds memory access
- Unexpected privilege escalation events in audit logs
Network Indicators:
- None - this is a local exploit
SIEM Query:
source="kernel" AND ("out of bounds" OR "segmentation fault") AND "mtk_wlan_ap"