Summary

• A vulnerability in the development shell (devshell) authentication for Cisco Aironet Series Access Points (APs) running the Cisco AP-COS operating system could allow an authenticated, local attacker to access the development shell without proper authentication, which allows for root access to the underlying Linux OS. The attacker would need valid device credentials.

  The vulnerability exists because the software improperly validates user-supplied input at the CLI authentication prompt for development shell access. An attacker could exploit this vulnerability by authenticating to the device and entering crafted input at the CLI. A successful exploit could allow the attacker to access the AP development shell without proper authentication, which allows for root access to the underlying Linux OS.

  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190417-aironet-shell

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products if they are running a vulnerable software release:

  • Aironet 1540 Series APs¹
  • Aironet 1560 Series APs²
  • Aironet 1800 Series APs³
  • Aironet 2800 Series APs
  • Aironet 3800 Series APs

  ¹For Aironet 1540 Series APs, the first supported release is 8.5.103.0.
  ²For Aironet 1560 Series APs, the first supported release is 8.3.111.0.
  ³For Aironet 1800i APs, the first supported release is 8.5.103.0.

  For information about which software releases are vulnerable, see the Fixed Software section of this advisory.

  Determining the Aironet Series AP Software Release

  To determine which version of Cisco Aironet Series AP Software is running on a device, administrators can use the controller web interface or the CLI.

  To use the web interface, log in to the web interface, choose Management > Software Update, and then refer to the release number that appears at the top of the page.

  To use the CLI, issue the show version command and then refer to the value in the AP Running Image field of the command output. The following example shows the command output for a device running software version 8.3.102.0:

  AP# show version
  .
  .
  .
  cisco AIR-AP3802E-B-K9 ARMv7 Processor rev 1 (v7l) with 1030528/668540K bytes of memory.
  Processor board ID RFDPP1BS497
  AP Running Image     : 8.3.102.0
  Primary Boot Image   : 8.3.102.0
  .
  .
  .

  Determining the Cisco WLC Software Release

  To determine which Cisco WLC Software release is running on a device, administrators can use the controller web interface or the CLI.

  To use the web interface, do the following:

  1. By using a browser, log in to the controller web interface.
  2. Click the Monitor tab.
  3. Click Summary in the left pane.
  4. Under Controller Summary, the Software Version field shows the release number of the software that is currently running on the device.

  To use the CLI, log in to the controller by using Telnet, issue the show sysinfo command, and then refer to the value in the Product Version field of the command output. The following example shows the command output for a device that is running Cisco WLC Software Release 8.3.102.0:

  (wlc)> show sysinfo
  
  Manufacturer's Name.............................. Cisco Systems Inc.
  Product Name..................................... Cisco Controller
  Product Version.................................. 8.3.102.0
  Bootloader Version............................... 1.0.1
  Field Recovery Image Version..................... 6.0.182.0
  Firmware Version................................. FPGA 1.3, Env 1.6, USB console 1.27
  Build Type....................................... DATA + WPS
  .
  .
  .

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

  Cisco has confirmed that this vulnerability does not affect the following Cisco products:

  • Aironet 1520 Series APs
  • Aironet 1530 Series APs
  • Aironet 1550 Series APs
  • Aironet 1570 Series APs
  • Wireless Controllers
  • Wireless LAN Controllers (WLCs)

  In addition, Cisco has confirmed that this vulnerability does not affect Cisco Aironet APs that are running Cisco Lightweight Access Point (LAP) Software or Cisco IOS Software.

Details

• Cisco Aironet APs running the Cisco AP-COS OS contain a debugging and troubleshooting mechanism known as devshell. This feature was designed to allow secure, controlled access to the underlying Linux OS and debugging information.
  

  The devshell feature can provide information that is not accessible through existing show or debug commands. Cisco development engineers can request low-level information through this feature without having to update the software running on a device. This can provide several advantages, such as allowing the collection of data without a reboot, which can lead to the loss of important values that indicate error state issues, delaying problem resolution.

  Access to the devshell feature must be explicitly authorized by the customer; Cisco personnel cannot access this feature without customer consent. Once enabled, the devshell feature restricts access to the Linux shell to ensure that no changes are made to critical system files.

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license: https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

  Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.

  When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.

  In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

  Customers Without Service Contracts

  Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC: https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

  Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.

  Fixed Releases

  Customers should upgrade to an appropriate release as indicated in the table in this section. To help ensure a complete upgrade solution, consider that this advisory is part of a collection that includes the following advisories:

  • cisco-sa-20190417-aironet-shell: Cisco Aironet Series Access Points Development Shell Access Vulnerability
  • cisco-sa-20190417-wlc-csrf: Cisco Wireless LAN Controller Software Cross-Site Request Forgery Vulnerability
  • cisco-sa-20190417-wlc-gui: Cisco Wireless LAN Controller Software GUI Configuration Denial of Service Vulnerabilities
  • cisco-sa-20190417-wlc-iapp: Cisco Wireless LAN Controller Software IAPP Message Handling Denial of Service Vulnerabilities

  In the following table, the left column lists major Cisco software releases. The center column indicates whether a major release is affected by the vulnerability described in this advisory and the first minor release that includes the fix for this vulnerability. The right column indicates whether a major release is affected by all the vulnerabilities described in this collection of advisories and which release includes fixes for those vulnerabilities.

  Cisco Aironet AP Software Major Release	First Fixed Release for This Vulnerability	Recommended Release for All Vulnerabilities Described in the Collection of Advisories
  Prior to 8.0	Not applicable	8.3.150.0
  8.0	Not applicable	8.3.150.0
  8.1	Not applicable	8.3.150.0
  8.2	8.3.150.0	8.3.150.0
  8.3	8.3.150.0	8.3.150.0
  8.4	8.5.135.0	8.5.140.0
  8.5	8.5.135.0	8.5.140.0
  8.6	8.8.100.0	8.8.120.0
  8.7	8.8.100.0	8.8.120.0
  8.8	8.8.100.0	8.8.120.0
  8.9	Not vulnerable	Not vulnerable

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

Source

• Cisco would like to thank Marcin Kopec and Hans Christian Rudolph of Deutsche Telekom for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190417-aironet-shell

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2019-April-17

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