Cisco ASA/Firepower Threat Defense Loopback Interface access control

Summaryinfo

A vulnerability classified as critical has been found in Cisco ASA and Firepower Threat Defense. This affects an unknown part of the component Loopback Interface Handler. This manipulation causes access control. The identification of this vulnerability is CVE-2025-20219. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Cisco ASA and Firepower Threat Defense (version now known) and classified as critical. Affected by this vulnerability is some unknown processing of the component Loopback Interface Handler. The manipulation with an unknown input leads to a access control vulnerability. The CWE definition for the vulnerability is CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

A vulnerability in the implementation of access control rules for loopback interfaces in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to send traffic that should have been blocked to a loopback interface. This vulnerability is due to improper enforcement of access control rules for loopback interfaces. An attacker could exploit this vulnerability by sending traffic to a loopback interface on an affected device. A successful exploit could allow the attacker to bypass configured access control rules and send traffic that should have been blocked to a loopback interface on the device.

It is possible to read the advisory at sec.cloudapps.cisco.com. This vulnerability is known as CVE-2025-20219 since 10/10/2024. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 08/17/2025). The attack technique deployed by this issue is T1068 according to MITRE ATT&CK.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2025-1839). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Cisco ASA (Adaptive Security Appliance)

Productinfo

Type

• Firewall Software

Vendor

• Cisco

Name

• ASA
• Firepower Threat Defense

License

• commercial

Website

• Vendor: https://www.cisco.com/

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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