Wednesday, December 11, 2019

Vulnerability Spotlight: Denial-of-service vulnerabilities in Linux kernel, W1.fi


Mitchell Frank and Mark Leonard of Cisco discovered these vulnerabilities. Blog by Jon Munshaw.

Cisco Talos recently discovered two denial-of-service vulnerabilities in the open-source program W1.fi. Both of these vulnerabilities target hostapd. One could allow an attacker to forge authentication requests, while another could trigger a deauthentication, both resulting in a denial of service.

In accordance with our coordinated disclosure policy, Cisco Talos worked with the manager of W1.fi to ensure that these issues are resolved and that an update is available for affected customers. TALOS-2019-0849 relates to TALOS-2019-0900, a denial-of-service vulnerability in the Linux kernel. Linux has also released an update to address that vulnerability, which makes more versions of Linux besides the mainline one safe from these vulnerabilities.

Vulnerability details

W1.fi hostapd CAM table denial-of-service vulnerability (TALOS-2019-0849/CVE-2019-5061)

An exploitable denial-of-service vulnerability exists in hostapd version 2.6. An attacker could exploit this vulnerability by triggering AP to send IAPP location updates for stations before the required authentication process has completed. This could lead to different denial-of-service scenarios, either by causing CAM table attacks, or by leading to traffic flapping if faking already existing clients in other nearby APs of the same wireless infrastructure. An attacker can forge Authentication and Association Request packets to trigger this vulnerability.

Read the complete vulnerability advisory here for additional information.

W1.fi hostapd deauthentication denial-of-service vulnerability (TALOS-2019-0850/CVE-2019-5062)

An exploitable denial-of-service vulnerability exists in the 802.11w security state handling for hostapd 2.6 connected clients with valid 802.11w sessions. By simulating an incomplete new association, an attacker can trigger a deauthentication against stations using 802.11w, resulting in a denial of service.

Read the complete vulnerability advisory here for additional information.

Linux kernel CAM table denial-of-service vulnerability (TALOS-2019-0900/CVE-2019-5108)

An exploitable denial-of-service vulnerability exists in the Linux kernel prior to mainline 5.3. An attacker could exploit this vulnerability by triggering AP to send IAPP location updates for stations before the required authentication process has completed. This could lead to different denial-of-service scenarios, either by causing CAM table attacks or by leading to traffic flapping if faking already existing clients in other nearby APs of the same wireless infrastructure. An attacker can forge Authentication and Association Request packets to trigger this vulnerability.

Read the complete vulnerability advisory here for additional information.

Versions tested

Talos tested and confirmed that TALOS-2019-0849 affects hostapd version 2.6 and Ubiquiti AP-AC-Pro firmware 4.0.10.9653. TALOS-2019-0850 affects hostapd version 2.6 when running on a Raspberry Pi. TALOS-2019-0900 affects versions 4.14.98-v7 and higher of the Linux operating system.


Coverage

The following SNORTⓇ rules will detect exploitation attempts. Note that additional rules may be released at a future date and current rules are subject to change pending additional vulnerability information. For the most current rule information, please refer to your Firepower Management Center or Snort.org.

Snort Rules: 50516

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