CVE-2026-68407: Linux Kernel WiFi Memory Leak Vulnerability

CVE-2026-68407 Overview

CVE-2026-68407 is a memory leak vulnerability in the Linux kernel's nl80211 wireless netlink interface. The flaw resides in nl80211_parse_beacon(), which handles beacon data parsing for Wi-Fi operations. When the function processes Enhanced Multi-BSSID Advertisement (EMA) Reduced Neighbor Report (RNR) data, it rejects requests where there are fewer RNR entries than Multiple BSSID (MBSSID) entries. However, before the fix, the rejected RNR allocation was not freed before returning the error, leaving allocated memory orphaned. Kernel maintainers have resolved the issue by freeing the RNR data on the mismatch error path.

Critical Impact
Repeated triggering of the mismatched configuration path can exhaust kernel memory, degrading system stability on affected Linux hosts using Wi-Fi with EMA/MBSSID beaconing.

Affected Products

Linux kernel versions containing the nl80211_parse_beacon() EMA/RNR parsing logic prior to the fix
Distributions shipping vulnerable stable kernel branches
Systems using cfg80211/nl80211 with Multi-BSSID and RNR beacon configuration

Discovery Timeline

2026-08-10 - CVE-2026-68407 published to NVD
2026-08-10 - Last updated in NVD database

Technical Details for CVE-2026-68407

Vulnerability Analysis

The vulnerability is a kernel memory leak in the wireless subsystem's netlink attribute parser. nl80211_parse_beacon() is responsible for validating and staging beacon configuration data passed from userspace via the nl80211 interface. During processing of EMA beacon templates, the function allocates memory for the RNR structure derived from NL80211_ATTR_EMA_RNR_ELEMS. It then compares the number of RNR entries against the number of MBSSID entries. When RNR entries are fewer than MBSSID entries, the function rejects the request as invalid and returns an error.

The defect is that the freshly allocated RNR buffer has not yet been attached to the beacon data structure at the point of rejection. The error path returned without releasing the allocation, leaking the kernel memory associated with the RNR entries. Each rejected request contributed additional unreclaimable memory to the kernel heap.

Root Cause

The root cause is a missing deallocation on an error return path [CWE-401: Missing Release of Memory after Effective Lifetime]. Ownership of the RNR allocation had not yet transferred to the beacon structure, so no later cleanup routine could release it.

Attack Vector

Triggering the leak requires the ability to submit nl80211 beacon configuration containing mismatched MBSSID and EMA RNR element counts. This is a local operation, typically requiring CAP_NET_ADMIN on the relevant network namespace. Repeated submissions can be used to progressively exhaust kernel memory, resulting in denial of service on the host.

No verified public exploit code is available. The corrective changes are published in the mainline and stable kernel git tree, including commits 07a95ec, 312c8b9, 6f919f2, fa9592e, and fb052a6.

Detection Methods for CVE-2026-68407

Indicators of Compromise

Gradual, unexplained growth in kernel slab allocations on hosts that manage Wi-Fi access-point workloads.
Repeated EINVAL returns from nl80211 beacon configuration operations correlating with rising memory usage.
Userspace daemons such as hostapd logging repeated failed EMA/MBSSID beacon updates.

Detection Strategies

Monitor /proc/slabinfo and /proc/meminfo for abnormal kernel memory growth on wireless infrastructure hosts.
Audit nl80211 netlink traffic for beacon configuration submissions where RNR element counts do not match MBSSID entry counts.
Track kernel version and patch level across the fleet to identify hosts running unpatched builds.

Monitoring Recommendations

Alert on sustained kernel slab growth trends over multi-day windows on Wi-Fi hosts.
Correlate hostapd and wpa_supplicant error logs with kernel memory pressure events.
Baseline expected nl80211 operation rates and flag anomalous configuration churn from privileged processes.

How to Mitigate CVE-2026-68407

Immediate Actions Required

Update to a Linux kernel build that includes the upstream fix referenced by commits 07a95ec, 312c8b9, 6f919f2, fa9592e, or fb052a6.
Apply vendor-supplied kernel security updates on all affected distributions and reboot to activate the patched kernel.
Restrict CAP_NET_ADMIN and access to the nl80211 netlink family to trusted service accounts only.

Patch Information

The fix ensures that nl80211_parse_beacon() releases the RNR allocation before returning the error when EMA RNR entries are fewer than MBSSID entries. Patched commits are available in the stable kernel tree: 07a95ec, 312c8b9, 6f919f2, fa9592e, and fb052a6. Consult your distribution's advisory for the specific backport that applies to your kernel series.

Workarounds

Where patching is not immediately feasible, avoid configuring EMA RNR beacon parameters until the kernel is updated.
Constrain which user-space daemons can issue nl80211 beacon updates by tightening capability grants and systemd service restrictions.
On hosts that do not require Wi-Fi access-point functionality, unload or blacklist the wireless AP stack to eliminate the exposed code path.

bash

# Verify running kernel version and confirm patch level
uname -r
# On Debian/Ubuntu systems, apply the vendor-supplied kernel update
sudo apt update && sudo apt install --only-upgrade linux-image-$(uname -r | sed 's/-generic//')
# On RHEL/CentOS/Fedora systems
sudo dnf update kernel && sudo reboot