CVE-2026-23363: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-23363 Overview

CVE-2026-23363 is an Out-of-Bounds Read vulnerability discovered in the Linux kernel's MediaTek mt76 WiFi driver, specifically affecting the mt7925 chipset. The vulnerability exists in the mt7925_mac_write_txwi_80211() function, where improper frame length validation before accessing management frame fields can result in out-of-bounds memory access.

This vulnerability affects systems using MediaTek mt7925 WiFi chipsets with vulnerable Linux kernel versions. The mt76 driver family is commonly used in modern laptops and embedded devices utilizing MediaTek wireless hardware.

Critical Impact

Potential out-of-bounds memory access in the WiFi driver could lead to information disclosure, system instability, or potential privilege escalation in kernel context.

Affected Products

• Linux kernel with mt76 WiFi driver (mt7925 chipset support)
• Systems using MediaTek mt7925 WiFi hardware
• Linux distributions shipping vulnerable kernel versions

Discovery Timeline

• 2026-03-25 - CVE-2026-23363 published to NVD
• 2026-03-25 - Last updated in NVD database

Technical Details for CVE-2026-23363

Vulnerability Analysis

The vulnerability resides in the mt7925_mac_write_txwi_80211() function within the MediaTek mt76 WiFi driver subsystem. This function is responsible for writing transmit wireless information (TXWI) headers for 802.11 management frames. The flaw occurs because the function accesses management frame header fields without first validating that the frame buffer contains sufficient data.

When processing malformed or truncated WiFi frames, the driver may read beyond the allocated buffer boundaries, potentially accessing adjacent kernel memory. This type of memory safety violation in kernel space is particularly concerning as it operates with elevated privileges.

Root Cause

The root cause is a missing boundary check in mt7925_mac_write_txwi_80211(). The function directly accesses management frame (mgmt) fields without verifying that the frame length is sufficient to contain the expected header structure. This is a classic input validation oversight that can be triggered when the driver processes frames with unexpected or malicious lengths.

The fix involves adding proper frame length validation before accessing the management frame fields, ensuring that the buffer contains the expected amount of data before dereferencing pointers into the frame structure.

Attack Vector

The attack vector for this vulnerability involves crafted WiFi frames being processed by the vulnerable driver. An attacker within wireless range could potentially send specially crafted 802.11 management frames with truncated lengths that trigger the out-of-bounds read when processed by mt7925_mac_write_txwi_80211().

The exploitation scenario would involve:

1. Attacker operating within WiFi range of the target device
2. Sending malformed management frames with incorrect length fields
3. Driver processing these frames without proper length validation
4. Out-of-bounds memory access occurring during TXWI header construction

Detection Methods for CVE-2026-23363

Indicators of Compromise

• Kernel oops or panic messages referencing mt7925_mac_write_txwi_80211 or the mt76 driver
• Unexpected system crashes when WiFi is active
• Kernel log entries indicating memory access violations in the mt76 subsystem
• KASAN (Kernel Address Sanitizer) reports for the mt76 driver module

Detection Strategies

• Monitor kernel logs (dmesg) for warnings or errors related to the mt76 WiFi driver
• Enable KASAN on development/test systems to detect out-of-bounds memory access
• Implement kernel module integrity monitoring to detect driver anomalies
• Review system crash dumps for call traces involving mt7925_mac_write_txwi_80211

Monitoring Recommendations

• Configure centralized logging for kernel-level events across systems with mt7925 WiFi hardware
• Deploy host-based intrusion detection to monitor for unusual WiFi driver behavior
• Establish baseline WiFi driver performance metrics to identify anomalies
• Enable kernel auditing subsystem for tracking driver-related security events

How to Mitigate CVE-2026-23363

Immediate Actions Required

• Update the Linux kernel to a patched version containing the security fix
• If updates are not immediately available, consider disabling WiFi on affected systems temporarily
• Monitor vendor security advisories for distribution-specific patches
• Review and apply kernel updates from your Linux distribution's security repositories

Patch Information

The vulnerability has been resolved through multiple kernel commits that add proper frame length validation before accessing management frame fields. The patches are available in the Linux kernel stable branches:

• Kernel Git Commit 22a6419a8b9
• Kernel Git Commit 2831a8c5745
• Kernel Git Commit 3356464e50e
• Kernel Git Commit c41a9abd6ae

Apply the appropriate patch for your kernel version to remediate this vulnerability.

Workarounds

• Disable WiFi functionality on affected systems if the mt7925 chipset is used and patching is not immediately possible
• Use wired Ethernet connections as an alternative until kernel updates can be applied
• Blacklist the mt7925 driver module (modprobe -r mt7925) if WiFi is not required
• Implement network segmentation to limit wireless attack surface exposure

# Temporarily disable mt7925 WiFi module (if WiFi not required)
sudo modprobe -r mt7925

# Add to blacklist for persistent disable
echo "blacklist mt7925" | sudo tee /etc/modprobe.d/blacklist-mt7925.conf

# Verify kernel version for patch status
uname -r