Background & Context

Cisco ASA 5500 Series Adaptive Security Appliances, ASA) is Cisco’s line of network security devices introduced in May 2005. Cisco ASA has become one of the most widely used firewall/VPN solutions for small to medium businesses. Cisco Secure Firewall Threat Defense (FTD) Virtual brings Cisco’s next-generation firewall functionalities to virtualized environments, enabling consistent security policies to follow workloads across your physical, virtual, and cloud environments, and between clouds.

Vulnerability Summary

A buffer tracking issue exists in Cisco firewalls when the software parses invalid URLs that are requested from the web services interface. By sending a crafted GET request to the web services interface, an unauthenticated, remote attacker could retrieve memory contents from an affected device.

Impact If Exploited

An attacker could exploit this vulnerability to retrieve memory contents, which could lead to the disclosure of confidential information. The sensitive data may include username and passwords which can be retrieved from the memory in clear text, allowing unauthorised remote access to the device in the context of the user whose credentials are obtained.

NOTE: This vulnerability has been reported by the CISA (America’s Cyber Defense Agency) to be known to be currently actively exploited in the wild as of 2024-02-15. Forensic data indicates that the Akira Ransomware group might be actively exploiting the vulnerability, which was originally disclosed on May 6, 2020. Akira is likely an offshoot from the now-defunct Conti ransomware syndicate that is known to have had ties to the FSB. Prioritisation should be given to remediation in any impacted environment

Affected Product Versions

Cisco Adaptive Security Appliance (ASA):

• Cisco ASA 9.x prior to release 9.51
• Cisco ASA 9.6 prior to release 9.6.4.41
• Cisco ASA 9.7 prior to release 9.71
• Cisco ASA 9.8 prior to release 9.8.4.20
• Cisco ASA 9.9 prior to release 9.9.2.67
• Cisco ASA 9.10 prior to release 9.10.1.40
• Cisco ASA 9.12 prior to release 9.12.3.9
• Cisco ASA 9.13 prior to release 9.13.1.10

Cisco Firepower Threat Defense (FTD):

• Cisco FTD 6,x prior to release 6.2.31
• Cisco FTD 6.2.3 prior to release 6.2.3.16
• Cisco FTD 6.3.0 prior to release 6.3.0.6
• Cisco FTD 6.4.0 prior to release 6.4.0.9
• Cisco FTD 6.5.0 prior to release 6.5.0.5

NOTE: This vulnerability affects only specific AnyConnect and WebVPN configurations.

Remediation

Official Fix & Remediation Guidance

Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. Customers are advised to upgrade to the latest version of the impacted Cisco ASA or FTD product.

Fixed versions:

Cisco Adaptive Security Appliance (ASA):

• Cisco ASA release 9.51
• Cisco ASA release 9.6.4.41
• Cisco ASA release 9.71
• Cisco ASA release 9.8.4.20
• Cisco ASA release 9.9.2.67
• Cisco ASA release 9.10.1.40
• Cisco ASA release 9.12.3.9
• Cisco ASA release 9.13.1.10

Cisco Firepower Threat Defense (FTD):

• Cisco FTD release 6.2.31
• Cisco FTD release 6.2.3.16
• Cisco FTD release 6.3.0.6
• Cisco FTD release 6.4.0.9
• Cisco FTD release 6.5.0.5

To upgrade to a fixed release of Cisco FTD Software, customers can do one of the following:

• For devices that are managed by using Cisco Firepower Management Center (FMC), use the FMC interface to install the upgrade. After installation is complete, reapply the access control policy.
• For devices that are managed by using Cisco Firepower Device Manager (FDM), use the FDM interface to install the upgrade. After installation is complete, reapply the access control policy.

NOTE: Remediation of this vulnerability by patching to a specific version indicated may not be sufficient to secure the product against further vulnerabilities discovered in later versions, subsequent to the publication of this guidance. Unless contra-indicated, customers are therefore advised to always upgrade to the latest version of the product available.

Temporary Mitigation & Workarounds:

For defense-in-depth:

• Implement MFA on all accounts and services where it is possible, especially for Client VPN connections.
• Enforce a password change, especially if there are accounts in the environment that have not changed password after the version upgrade.
• Change secrets and pre-shared keys in device configurations if they have not been changed after the version upgrade.
• Patch to a non-vulnerable version if not already done.
• Ensure logging is enabled.

NOTE: Caution should always be taken in applying any temporary mitigations listed. Mitigations are only recommended in cases where patches to remediate the vulnerability are not available, or cannot safely be applied to a given environment immediately. A given mitigation may not in all cases be recommended officially by the application vendor. The viability of any given temporary mitigation measure may vary, depending on server platform and existing configuration. Mitigations listed may incompletely remediate any given vulnerability. Configuration changes to implement listed mitigations may impact/disrupt required functionality within a given customer application. Care should therefore be taken to carefully analyse any listed mitigations for appropriateness to a given environment. Customers are advised to test any configuration changes prior to their being introduced into a production environment.

References:

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-info-disclose-9eJtycMB
• https://www.truesec.com/hub/blog/akira-ransomware-and-exploitation-of-cisco-anyconnect-vulnerability-cve-2020-3259

Category: Memory Access Violation

About AppCheck

AppCheck is a software security vendor based in the UK, offering a leading security scanning platform that automates the discovery of security flaws within organisations websites, applications, network, and cloud infrastructure. AppCheck are authorized by the Common Vulnerabilities and Exposures (CVE) Program as a CVE Numbering Authority (CNA).