CVE-2026-68402: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-68402 Overview

CVE-2026-68402 is an out-of-bounds read vulnerability in the Linux kernel's cfg80211 wireless configuration subsystem. The flaw resides in cfg80211_is_element_inherited(), which parses information elements from IEEE 802.11 management frames. A zero-length WLAN_EID_EXTENSION element causes the function to read one octet past the element's data buffer. An adjacent attacker operating a rogue access point can craft frames that trigger the read during Multi-Link element or non-transmitted BSS profile parsing. The bug was discovered through KASAN-instrumented fuzzing of ieee802_11_parse_elems_full().

Critical Impact
Adjacent attackers can trigger a slab-out-of-bounds read in the kernel's Wi-Fi stack, causing denial of service or potential information disclosure from kernel heap memory.

Affected Products

Linux kernel cfg80211 wireless subsystem (net/wireless/scan.c)
Linux distributions shipping vulnerable stable kernel branches prior to the referenced fix commits
Any system using the Linux kernel Wi-Fi stack for station-mode operation

Discovery Timeline

2026-08-10 - CVE-2026-68402 published to NVD
2026-08-13 - Last updated in NVD database

Technical Details for CVE-2026-68402

Vulnerability Analysis

The vulnerability is an out-of-bounds read [CWE-125] in the Linux kernel's cfg80211 subsystem. Specifically, cfg80211_is_element_inherited() in net/wireless/scan.c accesses elem->data[0] to obtain the extension element ID for lookup against a non-inheritance list. The function tests elem->id but never verifies that the element carries at least one data octet before dereferencing elem->data[0].

When _ieee802_11_parse_elems_full() processes a frame within a non-inheritance context, such as parsing a per-STA profile inside a Multi-Link element in a (re)association response or a non-transmitted BSS profile, the check runs against every element. A crafted frame containing a WLAN_EID_EXTENSION element of length zero triggers a one-byte slab-out-of-bounds read, flagged by KASAN as slab-out-of-bounds in cfg80211_is_element_inherited.

Root Cause

The root cause is missing length validation. The parser assumes an extension element always contains an extension ID octet, but the IEEE 802.11 frame format permits an attacker-controlled length field of zero. The fix returns early and treats the element as inherited when the extension element carries no data, mirroring the existing handling for empty ID lists.

Attack Vector

Exploitation requires adjacent network access. An attacker operating a malicious or compromised access point within Wi-Fi range sends a crafted management frame containing a Multi-Link element or a non-transmitted BSS profile. Inside that structure, an extension element with length zero is embedded. When the victim station parses the frame, the out-of-bounds read fires. No user interaction or authentication is required beyond the client attempting association or scanning.

No public proof-of-concept exploit code is available. The vulnerability was identified through kernel fuzzing under KASAN and disclosed through upstream stable-tree fix commits.

Detection Methods for CVE-2026-68402

Indicators of Compromise

KASAN reports in kernel logs referencing slab-out-of-bounds in cfg80211_is_element_inherited or nearby symbols in net/wireless/scan.c
Unexpected cfg80211 or mac80211 kernel warnings, oopses, or panics coinciding with Wi-Fi association or scan events
Repeated association or beacon frames from an unknown BSSID advertising Multi-Link or multi-BSSID elements

Detection Strategies

Enable KASAN on test and canary systems to surface out-of-bounds reads in the wireless stack during triage
Monitor dmesg and centralized log pipelines for kernel stack traces referencing cfg80211_is_element_inherited, _ieee802_11_parse_elems_full, or cfg80211_parse_ml_elem_sta_data
Compare running kernel versions against the fixed commits (11ac7a5, 20c308d, 84bd907, cb8afea, ddf2773) via configuration management tooling

Monitoring Recommendations

Ship kernel logs to a centralized SIEM or data lake and alert on wireless-subsystem crash signatures
Track wireless client crash and reboot patterns across fleets, correlating with location and SSID metadata
Monitor for rogue access points advertising malformed IEEE 802.11 elements using wireless intrusion detection sensors

How to Mitigate CVE-2026-68402

Immediate Actions Required

Apply the upstream Linux kernel patch or the corresponding stable-tree backport shipped by your distribution vendor
Inventory Linux endpoints, servers, and embedded devices that use the in-tree cfg80211 Wi-Fi stack and prioritize patching mobile and laptop fleets
Restrict connections to trusted, authenticated wireless networks and disable auto-join for open SSIDs where feasible

Patch Information

The vulnerability is fixed in the upstream Linux kernel via commits 11ac7a5, 20c308d, 84bd907, cb8afea, and ddf2773. The fix short-circuits cfg80211_is_element_inherited() when an extension element has zero data bytes, treating it as inherited. Apply the kernel update supplied by your Linux distribution's security advisories.

Workarounds

Disable Wi-Fi on affected systems in high-risk environments until a patched kernel is deployed
Enforce use of enterprise WPA2/WPA3-Enterprise networks with server certificate validation to reduce exposure to rogue APs
Where kernel updates are delayed, unload the cfg80211 and dependent Wi-Fi driver modules on systems that do not require wireless connectivity

bash

# Verify installed kernel version and check for the fix
uname -r

# Debian/Ubuntu: install the latest security-patched kernel
sudo apt update && sudo apt install --only-upgrade linux-image-generic

# RHEL/Fedora: update to a patched kernel package
sudo dnf update kernel

# Temporarily disable Wi-Fi where patching is not yet possible
sudo rfkill block wifi