CVE-2016-4476

What it actually does

The flaw permits newline and carriage return characters in WPS passphrase parameters, allowing malformed input to reach internal parsing routines and trigger an unhandled condition that terminates the hostapd or wpa_supplicant daemon.

Why it matters to the business

Wireless authentication services can be taken offline remotely, interrupting user network access and requiring manual restarts of affected access points or supplicants until the service is restored.

How an attack unfolds

An attacker within radio range crafts a WPS message containing embedded newline or carriage return characters in the passphrase field and transmits it to a vulnerable hostapd instance or wpa_supplicant client; the daemon fails to sanitize the input, causing an immediate crash and outage.

How to fix it

Upgrade hostapd and wpa_supplicant to versions later than 2.5 that enforce rejection of newline and carriage return characters in passphrase fields; disable WPS where it is not required as a temporary control.

How to confirm the fix worked

Confirm that current software versions exceed 2.5 and that test WPS operations containing \n or \r characters are rejected with an error rather than causing a process exit; review process monitoring to verify the daemon remains stable under malformed input.

Typical attack path

1. Locate a target device running an affected version of hostapd or wpa_supplicant with WPS enabled.
2. Craft a WPS association or credential message that injects \n or \r characters into the passphrase parameter.
3. Transmit the malformed message over the wireless medium.
4. Observe daemon termination and resulting loss of 802.1X or WPA functionality.

How to detect it

Inspect hostapd and wpa_supplicant logs for abrupt process exits or segmentation faults occurring during WPS operations; correlate with wireless frame captures showing unusual passphrase lengths or control characters in WPS messages.

What your security team should do

• Apply vendor updates that enforce strict passphrase character validation as soon as packages become available.
• Disable WPS on all production wireless infrastructure unless explicitly required.
• Implement process restart automation and alerting for hostapd/wpa_supplicant crashes.
• Monitor wireless traffic for anomalous WPS frames as a compensating control until patches are deployed.