Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H/E:X/RL:X/RC:X
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A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, remote attacker to cause a buffer overflow on an affected system.
The vulnerability is due to insufficient boundary checks for specific data that is provided to the web services interface of an affected system. An attacker could exploit this vulnerability by sending a malicious HTTP request. A successful exploit could allow the attacker to cause a buffer overflow condition on the affected system, which could disclose data fragments or cause the device to reload, resulting in a denial of service (DoS) condition.
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-memc-dos-fncTyYKGThis advisory is part of the April 2021 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: April 2021 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.
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Vulnerable Products
This vulnerability affects Cisco products if they are running a vulnerable release of Cisco ASA Software or FTD Software and have a vulnerable AnyConnect VPN or WebVPN configuration.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Vulnerable Configurations in Cisco ASA Software
In the following table, the left column lists the Cisco ASA Software features that are affected by this vulnerability. The right column indicates the basic configuration for the feature from the show running-config CLI command. If the device is configured for one of these features, it is considered vulnerable.
Cisco ASA Software Feature Vulnerable Configuration AnyConnect IKEv2 Remote Access
(with client services)crypto ikev2 enable <interface_name> client-services port <port #>
AnyConnect SSL VPN webvpn
enable <interface_name>Clientless SSL VPN webvpn
enable <interface_name>Vulnerable Configurations in Cisco FTD Software
In the following table, the left column lists the Cisco FTD Software features that are affected by this vulnerability. The right column indicates the basic configuration for the feature from the show running-config CLI command. If the device is configured for one of these features, it is considered vulnerable.
Cisco FTD Software Feature Vulnerable Configuration AnyConnect IKEv2 Remote Access
(with client services)1,2crypto ikev2 enable <interface_name> client-services port <port #>
AnyConnect SSL VPN1,2 webvpn
enable <interface_name>1.Remote Access VPN features are enabled through Devices > VPN > Remote Access in Cisco Firepower Management Center (FMC) or through Device > Remote Access VPN in Cisco Firepower Device Manager (FDM).2. Remote Access VPN features were first supported in Cisco FTD Software Release 6.2.2.
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 Cisco Firepower Management Center (FMC) Software.
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There are no workarounds that address this vulnerability.
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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.htmlAdditionally, 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 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
In the following table(s), the left column lists Cisco software releases. The center column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. The right column indicates whether a release is affected by any of the vulnerabilities described in this bundle and which release includes fixes for those vulnerabilities.
ASA Software
Cisco ASA Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories Earlier than 9.81 Not vulnerable Migrate to a fixed release. 9.8 9.8.4.34 9.8.4.35 9.9 9.9.2.85 9.9.2.85 9.101 Migrate to a fixed release. Migrate to a fixed release. 9.12 9.12.4.13 9.12.4.18 9.13 9.13.1.21 9.13.1.21 9.14 9.14.2.8 9.14.2.13 9.15 9.15.1.7 9.15.1.15 1. Cisco ASA Software releases 9.7 and earlier, as well as Release 9.10, have reached end of software maintenance. Customers are advised to migrate to a supported release that includes the fix for this vulnerability.
FTD Software
Cisco FTD Software Release First Fixed Release for This Vulnerability Recommended Fixed Release for All Vulnerabilities Described in the Bundle of Advisories Earlier than 6.2.21 Migrate to a fixed release. Migrate to a fixed release. 6.2.2 Migrate to a fixed release. Migrate to a fixed release. 6.2.3 Migrate to a fixed release. Migrate to a fixed release. 6.3.0 Migrate to a fixed release. Migrate to a fixed release. 6.4.0 6.4.0.12 (May 2021) 6.4.0.12 (May 2021) 6.5.0 Migrate to a fixed release. Migrate to a fixed release. 6.6.0 6.6.32 6.6.42 6.7.0 6.7.0.1 6.7.0.2 1. Cisco FMC and FTD Software releases 6.0.1 and earlier, as well as releases 6.2.0 and 6.2.1, have reached end of software maintenance. Customers are advised to migrate to a supported release that includes the fix for this vulnerability.
2. The First Fixed Release for the 6.6.0 code train was 6.6.3; however, due to upgrade issues associated with CSCvx86231 the recommended release is 6.6.4.
To upgrade to a fixed release of Cisco FTD Software, 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.
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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.
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Cisco would like to thank Joshua Perez and Phil Purviance for reporting this vulnerability.
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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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Show LessVersion Description Section Status Date 1.1 Updated internal link to the Fixed Software section. Vulnerable Products Final 2021-MAY-04 1.0 Initial public release. — Final 2021-APR-28
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