CVE-2026-64515: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-64515 Overview

CVE-2026-64515 is a Linux kernel vulnerability in the mac80211 wireless subsystem. The flaw affects Multi-Link Element (MLE) defragmentation handling for reconfiguration and Enhanced Point-to-Point Coordination Set (EPCS) elements contained in non-transmitted profiles. The defragmentation routine receives a pointer to the defragmented copy but continues parsing from the original elements, leading to incorrect data handling and potential heap buffer overruns.

An adjacent attacker within wireless range can trigger the issue by transmitting crafted 802.11 management frames. The vulnerability impacts kernel memory integrity and system availability.

Critical Impact
Adjacent network attackers can trigger heap data overrun in the Linux kernel's mac80211 subsystem through crafted Multi-Link Element frames, potentially causing memory corruption and denial of service.

Affected Products

Linux kernel mac80211 wireless subsystem
Kernel branches referenced in stable commits 1f573e17, 55c479aa, 722b3f86, and a74e893f
Systems using Wi-Fi 7 Multi-Link Operation (MLO) with reconfiguration or EPCS support

Discovery Timeline

2026-07-25 - CVE-2026-64515 published to NVD
2026-07-27 - Last updated in NVD database

Technical Details for CVE-2026-64515

Vulnerability Analysis

The vulnerability resides in the mac80211 MLE parsing logic within the Linux kernel wireless stack. When either a reconfiguration MLE or an EPCS MLE is encountered inside a non-transmitted profile, the defragmentation routine is invoked with a pointer that references the defragmented copy. However, the surrounding parsing code continues to operate against the original elements rather than the defragmented buffer.

This mismatch produces two distinct failure modes. First, when defragmentation was actually required, subsequent parsing cannot locate the correct reassembled data. Second, when the original frame resides at a higher memory address than the defragmentation buffer, parsing may overrun into adjacent heap data. The overrun is bounded by the new defragmentation buffer layout, where parsing stops once the buffer fills with copied data.

The fix tracks the container alongside the element pointer and unifies the two nearly identical defragmentation routines into a single implementation.

Root Cause

The root cause is an inconsistent pointer reference between the defragmentation helper and its callers in the non-transmitted profile parsing path. The caller passes the defragmented copy to the helper but retains references to the original element for continued parsing, producing an Out-of-Bounds Read condition on the kernel heap.

Attack Vector

Exploitation requires adjacent network access, meaning the attacker must be within wireless radio range of the target. No authentication or user interaction is required. An attacker constructs 802.11 beacon or probe response frames that embed a non-transmitted profile containing a fragmented reconfiguration or EPCS Multi-Link Element. The target kernel processes the frame during normal Wi-Fi scanning or association operations.

For complete technical details, refer to the upstream fix commits:

Detection Methods for CVE-2026-64515

Indicators of Compromise

Unexpected kernel oops or panic messages referencing ieee80211_mle_parse_link_id, ieee80211_defragment_element, or related mac80211 symbols in dmesg
KASAN (Kernel Address Sanitizer) reports indicating slab-out-of-bounds reads within mac80211 parsing routines
Wireless interface resets or driver restarts coinciding with reception of unusual beacon or probe response frames

Detection Strategies

Monitor kernel ring buffers and journal logs for mac80211 warnings, WARN_ON traces, and unexpected NULL pointer or heap corruption stack traces
Capture 802.11 frames in monitor mode and inspect for oversized or fragmented Multi-Link Elements in non-transmitted profiles
Correlate host telemetry with proximity events such as unknown SSIDs broadcasting Wi-Fi 7 capability advertisements

Monitoring Recommendations

Deploy endpoint telemetry that captures kernel crash dumps and forwards them for centralized analysis
Track kernel versions across the fleet and flag hosts running unpatched branches that received the fix commits
Alert on repeated wireless driver crashes on the same host within short time windows, which may indicate active probing

How to Mitigate CVE-2026-64515

Immediate Actions Required

Apply the upstream Linux kernel patches referenced in the stable commits 1f573e17, 55c479aa, 722b3f86, and a74e893f as soon as vendor packages are available
Update to distribution-provided kernel packages that include the mac80211 MLE defragmentation fix
Prioritize patching for laptops, mobile workstations, and any Linux endpoints operating in untrusted wireless environments

Patch Information

The fix unifies the two defragmentation routines and tracks the container alongside the element pointer, ensuring parsing operates on the correct buffer. Rebuild and deploy the kernel from any of the referenced stable commits, or install the corresponding distribution security update once published by your Linux vendor.

Workarounds

Disable Wi-Fi radios on Linux systems that do not require wireless connectivity until patches are applied
Restrict wireless client operation to trusted, controlled SSIDs and disable automatic scanning where feasible
Unload the mac80211 module and dependent wireless drivers on servers or appliances that have no operational need for Wi-Fi

bash

# Verify kernel version and check for the mac80211 module
uname -r
lsmod | grep mac80211

# Temporarily disable wireless interfaces until patched
sudo nmcli radio wifi off

# Optional: blacklist the wireless driver on systems that do not need Wi-Fi
echo "blacklist mac80211" | sudo tee /etc/modprobe.d/disable-mac80211.conf
sudo update-initramfs -u