CVE-2025-71234: Linux Kernel Buffer Overflow Vulnerability

CVE-2025-71234 Overview

A slab-out-of-bounds write vulnerability has been identified in the Linux kernel's rtl8xxxu WiFi driver. The issue occurs because the driver fails to properly set hw->sta_data_size, causing the mac80211 subsystem to allocate insufficient memory for driver-private station data in __sta_info_alloc(). When the rtl8xxxu_sta_add() function accesses members of struct rtl8xxxu_sta_info through sta->drv_priv, this results in an out-of-bounds write to slab memory.

Critical Impact

Local attackers could potentially exploit this memory corruption vulnerability to cause system instability, denial of service, or potentially escalate privileges through kernel memory corruption on systems using RTL8xxxU-based WiFi adapters.

Affected Products

• Linux kernel with rtl8xxxu WiFi driver enabled
• Systems using RTL8192EU and compatible RTL8xxxU WiFi adapters
• RISC-V platforms including StarFive VisionFive 2 boards

Discovery Timeline

• 2026-02-18 - CVE CVE-2025-71234 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2025-71234

Vulnerability Analysis

This vulnerability stems from a driver initialization oversight in the rtl8xxxu WiFi driver. The mac80211 wireless networking stack in Linux relies on drivers to specify the size of their per-station private data structures through the hw->sta_data_size field. When this value is not set, mac80211 allocates station information structures without accounting for the driver's private data needs.

The KASAN (Kernel Address Sanitizer) report captured on a RISC-V platform (VisionFive 2) with an RTL8192EU adapter demonstrates the issue clearly - an 8-byte write occurs beyond the allocated slab boundary during station addition operations. This type of memory corruption in kernel space can lead to unpredictable system behavior, crashes, or potential security compromises.

Root Cause

The root cause is the missing initialization of hw->sta_data_size in the driver's probe function. While the driver correctly sets hw->vif_data_size for virtual interface private data, it neglects to set the corresponding value for per-station private data. This asymmetric configuration leads mac80211 to allocate structures that are too small to accommodate struct rtl8xxxu_sta_info, the driver's per-station data structure.

Attack Vector

The attack vector requires local access to a system running the vulnerable kernel with an RTL8xxxU-based WiFi adapter. The vulnerability is triggered during normal WiFi operations when stations are added to the network interface. An attacker with the ability to influence WiFi station management operations could potentially exploit this memory corruption to:

1. Cause kernel panics leading to denial of service
2. Corrupt adjacent kernel memory structures
3. Potentially achieve code execution in kernel context through heap manipulation techniques

The vulnerability does not require special privileges beyond the ability to trigger WiFi station management, which may occur through normal network operations or could be influenced by an attacker on the same wireless network.

Detection Methods for CVE-2025-71234

Indicators of Compromise

• KASAN reports indicating slab-out-of-bounds writes in rtl8xxxu_sta_add function
• Kernel crash dumps or oops messages referencing the rtl8xxxu driver
• Unexpected system instability when using RTL8xxxU WiFi adapters
• Memory corruption warnings in kernel logs related to mac80211 or rtl8xxxu modules

Detection Strategies

• Enable KASAN (Kernel Address Sanitizer) on systems where security monitoring is critical to detect out-of-bounds memory access
• Monitor kernel logs for BUG reports mentioning rtl8xxxu_sta_add or related functions
• Implement kernel module auditing to track rtl8xxxu driver loading and operation
• Deploy runtime integrity monitoring solutions that can detect anomalous kernel memory behavior

Monitoring Recommendations

• Configure centralized logging for kernel messages across affected systems
• Set up alerting for KASAN violation reports in kernel logs
• Monitor WiFi adapter enumeration and driver loading events
• Track kernel module versions to identify systems running vulnerable driver code

How to Mitigate CVE-2025-71234

Immediate Actions Required

• Update to a patched Linux kernel version that includes the fix for hw->sta_data_size initialization
• If immediate patching is not possible, consider temporarily disabling or removing RTL8xxxU WiFi adapters from affected systems
• Review systems for signs of exploitation by examining kernel logs for KASAN reports
• Prioritize patching for RISC-V systems and embedded devices using RTL8xxxU adapters

Patch Information

The vulnerability has been resolved in the Linux kernel stable branches. The fix sets hw->sta_data_size to sizeof(struct rtl8xxxu_sta_info) during the driver's probe sequence, ensuring mac80211 allocates sufficient space for the driver's per-station private data.

Patch commits are available:

• Kernel Git Commit 116f7bd
• Kernel Git Commit 5d810ba
• Kernel Git Commit 9a0f3fa

Workarounds

• Blacklist the rtl8xxxu kernel module on systems where the WiFi adapter is not required
• Use alternative WiFi adapters with different chipsets that do not rely on the affected driver
• On systems where the adapter is essential, limit network exposure and avoid untrusted wireless networks until patching is possible
• Enable KASAN for early detection of exploitation attempts in development or testing environments

# Blacklist the vulnerable driver if not needed
echo "blacklist rtl8xxxu" | sudo tee /etc/modprobe.d/blacklist-rtl8xxxu.conf
sudo update-initramfs -u
sudo reboot