CVE-2026-23246: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-23246 Overview

A stack out-of-bounds write vulnerability has been identified in the Linux kernel's wifi mac80211 subsystem, specifically within the ieee80211_ml_reconfiguration function. The vulnerability arises from insufficient bounds checking of the link_id parameter extracted from ML Reconfiguration elements, potentially allowing values that exceed the array bounds of link_removal_timeout[].

Critical Impact

Attackers may exploit this out-of-bounds write to corrupt stack memory, potentially leading to kernel crashes, denial of service, or arbitrary code execution within the kernel context.

Affected Products

• Linux Kernel (wifi mac80211 subsystem)
• Systems using Multi-Link (ML) wifi reconfiguration functionality
• Devices with IEEE 802.11 wireless networking support

Discovery Timeline

• March 18, 2026 - CVE-2026-23246 published to NVD
• March 18, 2026 - Last updated in NVD database

Technical Details for CVE-2026-23246

Vulnerability Analysis

This vulnerability exists in the Linux kernel's mac80211 wireless networking subsystem, which handles IEEE 802.11 protocol implementation. The flaw specifically affects the Multi-Link (ML) reconfiguration handling code in the ieee80211_ml_reconfiguration function.

The core issue stems from how the kernel processes ML Reconfiguration elements received in wireless frames. The link_id value is extracted using a bitwise AND operation (control & 0x000f), which produces values ranging from 0 to 15. However, the link_removal_timeout[] array is sized based on IEEE80211_MLD_MAX_NUM_LINKS, which is defined as 15 elements. This creates an off-by-one vulnerability where a link_id of 15 would access index 15, which is beyond the valid array bounds (indices 0-14).

Root Cause

The root cause is a classic boundary condition error where the input validation fails to account for the mismatch between the possible input range (0-15) and the valid array indices (0-14). The link_id extracted from the ML Reconfiguration element's control field can represent up to 16 different values using 4 bits, but the corresponding array only accommodates 15 elements.

Attack Vector

The vulnerability can be triggered through crafted wireless frames containing malicious ML Reconfiguration elements. An attacker within wireless range could transmit specially crafted frames with a link_id value of 15, causing the kernel to write beyond the bounds of the link_removal_timeout[] array on the stack.

The exploitation mechanism involves:

1. Crafting an ML Reconfiguration element with the control field's lower 4 bits set to 0x0f (decimal 15)
2. Transmitting this malicious frame to a vulnerable system
3. When the kernel processes this frame, it writes to an out-of-bounds stack location

The fix implemented in the kernel patches adds proper bounds checking to skip subelements where link_id >= IEEE80211_MLD_MAX_NUM_LINKS, preventing the out-of-bounds access. For technical implementation details, see the kernel git commit.

Detection Methods for CVE-2026-23246

Indicators of Compromise

• Kernel panic or crash logs referencing ieee80211_ml_reconfiguration function
• Stack corruption warnings in kernel dmesg output related to mac80211 subsystem
• Unexplained wireless connectivity issues following suspicious wireless activity
• KASAN (Kernel Address SANitizer) reports indicating stack out-of-bounds access in wifi modules

Detection Strategies

• Enable KASAN in kernel debug builds to detect out-of-bounds memory access attempts
• Monitor kernel logs for stack buffer overflow warnings in the mac80211 module
• Implement wireless intrusion detection systems (WIDS) to identify anomalous ML Reconfiguration frames
• Deploy kernel tracing to monitor ieee80211_ml_reconfiguration function calls with boundary violations

Monitoring Recommendations

• Configure system monitoring to alert on kernel crashes or panics involving wifi subsystems
• Review wireless frame captures for ML Reconfiguration elements with link_id values of 15
• Implement runtime kernel integrity checking to detect stack corruption

How to Mitigate CVE-2026-23246

Immediate Actions Required

• Update the Linux kernel to a patched version containing the bounds-check fix
• Monitor kernel security advisories for your distribution's specific patch releases
• Consider temporarily disabling Multi-Link wifi functionality if patches are not immediately available
• Ensure wireless network segmentation to limit exposure to potentially malicious frames

Patch Information

Multiple kernel patches have been released to address this vulnerability. The fix adds bounds checking to skip subelements with link_id >= IEEE80211_MLD_MAX_NUM_LINKS, preventing the out-of-bounds write condition.

Patch commits are available at:

• Kernel Git Commit 162d331d
• Kernel Git Commit bfde158d
• Kernel Git Commit d58d71c2
• Kernel Git Commit f35ceec5

Workarounds

• Disable ML (Multi-Link) reconfiguration functionality if not required for your wireless deployment
• Implement network-level filtering to drop suspicious wireless management frames
• Use wireless access points with updated firmware that validates ML Reconfiguration elements
• Deploy additional network monitoring at the wireless layer to detect exploitation attempts

# Check current kernel version for vulnerability assessment
uname -r

# Monitor for mac80211 related kernel messages
dmesg | grep -i mac80211

# Check if Multi-Link wifi features are enabled
grep -r "IEEE80211_MLD" /boot/config-$(uname -r)