Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software DHCP Denial of Service Vulnerability – Source:sec.cloudapps.cisco.com

Medium

Summary

• A vulnerability in the DHCP client functionality of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, adjacent attacker to exhaust available memory.

  This vulnerability is due to improper validation of incoming DHCP packets. An attacker could exploit this vulnerability by repeatedly sending crafted DHCPv4 packets to an affected device. A successful exploit could allow the attacker to exhaust available memory, which would affect availability of services and prevent new processes from starting, resulting in a Denial of Service (DoS) condition that would require a manual reboot.

  Note: On Cisco Secure FTD Software, this vulnerability does not affect management interfaces.

  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-dhcp-qj7nGs4N

  This advisory is part of the August 2025 release of the Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: August 2025 Semiannual Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software Security Advisory Bundled Publication.

Affected Products

• At the time of publication, this vulnerability affected devices that had the DHCP client feature enabled and were running a vulnerable release of Cisco Secure Firewall ASA Software or Secure FTD Software.

  Note: On Cisco Secure FTD Software, this vulnerability affected only data interfaces. DHCP traffic that is received on the dedicated management interface cannot trigger this vulnerability.

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

  Determine Whether a Secure Firewall ASA Device Has the DHCP Client Feature Enabled

  To determine whether a device that is running Cisco Secure Firewall ASA Software has the DHCP client enabled on an interface, use the show ip | include DHCP command and look for lines that contain DHCP. The following example shows the output for a Cisco ASA device that has the DHCP client enabled on the GigabitEthernet0/3 interface:

  firewall# show ip | include DHCP
  GigabitEthernet0/3                              unassigned      unassigned      DHCP
  GigabitEthernet0/3                              unassigned      unassigned      DHCP
  firewall#  

  If this command returns empty output, the device is not affected by this vulnerability.

  Determine Whether a Secure Firewall ASA Device Is Configured as a DHCP Client

  To determine whether a device that is running Cisco Secure Firewall ASA Software has a DHCP client configured, use the show running-config | include address dhcp command. The following example shows the output for a Cisco Secure Firewall ASA device that has the DHCP client configured on an interface:

  ciscoasa# show running-config | include address dhcp
   ip address dhcp
  ciscoasa#

  If this command returns empty output, the device is not affected by this vulnerability.

  Determine Whether a Secure FTD Device Has the DHCP Client Feature Enabled

  To determine whether a device that is running Cisco Secure FTD Software has the DHCP client enabled on a data interface, use the following steps:

  1. Open the Cisco Secure Firewall Device Manager (FDM) user interface by accessing the management IP of the device through a web browser.
  2. Navigate to Interfaces > View All Interfaces.
  3. For each data interface, click the Edit icon. If the Type value is set to DHCP, that interface is configured as a DHCP client.

  If the interface is enabled, the device is affected by this vulnerability.

  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 Cisco Secure Firewall Management Center (FMC) Software.

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• 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.

  Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software

  To help customers determine their exposure to vulnerabilities in Cisco Secure Firewall ASA, Secure FMC, and Secure 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 Secure Firewall ASA Software or 6.6.7 for Cisco Secure FTD Software.
  5. Click Check.

  For instructions on upgrading a Cisco Secure FTD device, see the appropriate Cisco Secure FMC upgrade guide.

  Additional Resources

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

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

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

• This vulnerability was found during internal security testing by Jason Crowder of the Cisco Advanced Security Initiatives Group (ASIG).

Cisco Security Vulnerability Policy

• To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.

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Related to This Advisory

• Cisco Event Response: August 2025 Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software Security Advisory Bundled Publication

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-dhcp-qj7nGs4N

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	–	Final	2025-AUG-14

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