Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X
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A vulnerability in the AnyConnect SSL VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, remote attacker to send packets with another VPN user's source IP address.
This vulnerability is due to improper validation of the packet's inner source IP address after decryption. An attacker could exploit this vulnerability by sending crafted packets through the tunnel. A successful exploit could allow the attacker to send a packet impersonating another VPN user's IP address. It is not possible for the attacker to receive return packets.
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-asa-ssl-vpn-Y88QOm77
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Vulnerable Products
At the time of publication, this vulnerability affected Cisco ASA Software and FTD Software if it had the AnyConnect SSL VPN feature enabled. The AnyConnect clientless SSL VPN feature is not affected.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine the Cisco ASA Software Configuration
To determine whether Cisco ASA Software has the AnyConnect SSL VPN feature enabled, use the show running-config webvpn privileged EXEC command. The following example shows the output of the command for a device that has the AnyConnect SSL VPN feature enabled:
ciscoasa# show running-config webvpn
webvpn
enable interface_name
.
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.Determine the Cisco FTD Software Configuration
To determine whether Cisco FTD Software has the AnyConnect SSL VPN1,2 feature enabled, use the show running-config webvpn privileged EXEC command. The following example shows the output of the command for a device that has the AnyConnect SSL VPN feature enabled:
ciscoftd# show running-config webvpn
webvpn
enable interface_name
.
.
.1. Remote Access VPN features were introduced in Cisco FTD Software Release 6.2.2.
2. Remote Access VPN features can be enabled using Devices > VPN > Remote Access in Cisco Firepower Management Center (FMC) or using Device > Remote Access VPN in Cisco Firepower Device Manager (FDM).
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 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.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.
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:
- Choose which advisories the tool will search—all advisories, only advisories with a Critical or High Security Impact Rating (SIR), or only this advisory.
- Choose the appropriate software.
- Choose the appropriate platform.
- Enter a release number—for example, 9.16.2.11 for Cisco ASA Software or 6.6.7 for Cisco FTD Software.
- Click Check.
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
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The Cisco Product Security Incident Response Team (PSIRT) is aware of public announcements about the vulnerability that is described in this advisory.
The Cisco PSIRT is not aware of any malicious use of the vulnerability that is described in this advisory.
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Cisco would like to thank Ta-Lun Yen 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 1.0 Initial public release. — Final 2023-DEC-05
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