CVE-2019-16746

What it actually does

The flaw is a missing length check on variable-length elements inside a beacon head structure in the kernel wireless stack, allowing an attacker-supplied frame to write past the end of a stack or heap buffer.

Why it matters to the business

Remote attackers can crash wireless-enabled systems or execute arbitrary code with kernel privileges, leading to loss of availability, data exposure, or full host compromise on any device using the affected kernel code.

How an attack unfolds

An attacker crafts a malicious 802.11 beacon frame containing an oversized information element, transmits it to a target within radio range or via a rogue access point, and triggers the unchecked copy inside nl80211.c, resulting in memory corruption that can be turned into code execution.

How to fix it

Upgrade to a kernel containing the length validation fix for the beacon head parsing routine; apply vendor backports if running a supported distribution series; disable unnecessary wireless interfaces until patches are deployed.

How to confirm the fix worked

Confirm the running kernel version is newer than 5.2.17 and contains the commit that adds explicit length checks before copying variable beacon elements; review wireless driver source for the bounds test on nl80211 beacon parsing.

Typical attack path

1. Position a wireless transmitter within range of the victim or compromise a nearby access point
2. Transmit a beacon frame with a variable element whose length exceeds the kernel's assumed maximum
3. Trigger the nl80211 parsing path that copies the element without bounds checking
4. Leverage the resulting buffer overflow for kernel-level read/write or control-flow hijacking
5. Install persistence, exfiltrate data, or launch further attacks from the compromised host

How to detect it

Search kernel logs and wireless event traces for repeated oversized beacon frames or unexpected crashes in the nl80211 or cfg80211 modules; correlate with wireless interface activity around the time of any kernel oops or panic.

What your security team should do

• Prioritize patching all systems that expose the 802.11 stack to untrusted networks
• Monitor EPSS trend and any new exploit publications for increased urgency
• Temporarily disable wireless radios on high-value assets if immediate updates are not feasible
• Add kernel hardening features such as stack canaries and KASLR if not already enabled