Summary

• A vulnerability in the management and VPN web servers for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition.

  This vulnerability is due to incomplete error checking when parsing an HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to a targeted web server on a device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.

  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-asaftd-websrvs-dos-X8gNucD2

  For more information on the vulnerability that is described in this advisory, see Cisco Event Response: Attacks Against Cisco Firewall Platforms.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco ASA Software and FTD Software if they have one or more of the vulnerable configurations listed in the following two tables.

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

  Determine Whether an ASA or FTD Device Is Affected

  To determine whether a device that is running Cisco ASA Software or FTD Software is affected, use the show asp table socket | include SSL command and look for an SSL listen socket on any TCP port. If a socket is present in the output, the device should be considered vulnerable. The following example shows the output for a Cisco ASA device with two SSL listen sockets on TCP port 443 and TCP port 8443:

  ciscoasa#  show asp table socket | include SSL
  SSL       00185038  LISTEN     172.16.0.250:443    0.0.0.0:*
  SSL       00188638  LISTEN      10.0.0.250:8443    0.0.0.0:*   

  ASA Software Vulnerable Configuration

  In the following table, the left column lists Cisco ASA Software features that are potentially vulnerable. The right column indicates the basic configuration for the feature from the show running-config CLI command, if it can be determined. These features could cause the SSL listen sockets to be enabled.

  Cisco ASA Software Feature	Possible Vulnerable Configuration
  AnyConnect IKEv2 Remote Access (with client services)	crypto ikev2 enable [...] client-services port <port-number>
  Local Certificate Authority (CA)1	crypto ca server  no shutdown
  Management Web Server Access (including ASDM and CSM)2	http server enable http
  Mobile User Security (MUS)	webvpn  mus password  mus server enable port  mus
  REST API3	rest-api image disk0:/rest-api agent
  SSL VPN	webvpn  enable

  1. In Cisco ASA Software Release 9.13 and later, Local CA is deprecated and has been removed.

  2. Management Web Server Access would only be vulnerable from an IP address in the configured http command range.

  3. REST API is vulnerable only from an IP address in the configured http command range.

  FTD Software Vulnerable Configuration

  In the following table, the left column lists Cisco FTD Software features that are potentially vulnerable. The right column indicates the basic configuration for the feature from the show running-config CLI command, if it can be determined. These features could cause the SSL listen sockets to be enabled.

  Cisco FTD Software Feature	Possible Vulnerable Configuration
  AnyConnect IKEv2 Remote Access (with client services)1,2	crypto ikev2 enable [...] client-services port <port-number>
  AnyConnect SSL VPN1,2	webvpn  enable
  HTTP server enabled3	http server enable http

  1. Remote access VPN features are enabled from Devices > VPN > Remote Access in Cisco Firepower Management Center (FMC) Software or from Device > Remote Access VPN in Cisco Firepower Device Manager (FDM).

  2. Remote access VPN features are first supported as of Cisco FTD Software Release 6.2.2.

  3. The HTTP feature is enabled from Firepower Threat Defense Platform Settings > HTTP in the Cisco FMC Console.

  Products Confirmed Not Vulnerable

  Only products and services 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 Cisco FMC Software.

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 with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.

  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.

  The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.

  When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories 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.

  Cisco ASA, FMC, and FTD Software

  To help customers determine their exposure to vulnerabilities in Cisco ASA, FMC, and FTD Software, Cisco provides the Cisco Software Checker. This tool identifies any Cisco security advisories that impact a specific software release and the earliest release that fixes the vulnerabilities that are described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities that are described in all the advisories that the Software Checker identifies (“Combined First Fixed”).

  To use the tool, go to the Cisco Software Checker page and follow the instructions. Alternatively, use the following form to search for vulnerabilities that affect a specific software release. To use the form, follow these steps:

  1. Choose which advisories the tool will search—all advisories, only advisories with a Critical or High Security Impact Rating (SIR), or only this advisory.
  2. Choose the appropriate software.
  3. Choose the appropriate platform.
  4. Enter a release number—for example, 9.16.2.11 for Cisco ASA Software or 6.6.7 for Cisco FTD Software.
  5. Click Check.

  Only this advisory All Critical and High advisories All advisories Cisco ASA Software Cisco FMC Software Cisco FTD Software Any Platform 3000 Series Industrial Security Appliances (ISA) ASA 5500-X Series Firewalls ASA Service Module Adaptive Security Virtual Appliance (ASAv) Firepower 1000 Series Firepower 2100 Series Firepower 4100 Series Firepower 9000 Series Secure Firewall 3100 Series

   

  For instructions on upgrading an FTD device, see Cisco Firepower Management Center Upgrade Guide.

   

  Additional Resources

  For help determining the best Cisco ASA, FMC, or FTD Software release, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

  Cisco ASA Compatibility
  Cisco Secure Firewall ASA Upgrade Guide
  Cisco Secure Firewall Threat Defense Compatibility Guide

Exploitation and Public Announcements

• Cisco has confirmed that this vulnerability has been exploited. Cisco strongly recommends that customers upgrade to fixed software to resolve this vulnerability. Customers are also strongly encouraged to monitor system logs for indicators of undocumented configuration changes, unscheduled reboots, and any anomalous credential activity.

Source

• Cisco would like to thank the following organizations for supporting this investigation:

  • Australian Signals Directorate's Australian Cyber Security Centre
  • Canadian Centre for Cyber Security, a part of the Communications Security Establishment
  • The UK's National Cyber Security Centre (NCSC)
  • U.S. Cybersecurity & Infrastructure Security Agency (CISA)

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-websrvs-dos-X8gNucD2

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2024-APR-24

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