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AUSCERT External Security Bulletin Redistribution
ESB-2024.2551.2
Cisco Adaptive Security Appliance and Firepower Threat Defense Software Web
Services Denial of Service Vulnerability
26 April 2024
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AusCERT Security Bulletin Summary
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Product: Cisco Adaptive Security Appliance and Firepower Threat Defense Software Web Services
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2024-20353
Original Bulletin:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-websrvs-dos-X8gNucD2
Comment: CVSS (Max): 8.6 CVE-2024-20353 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
CVSS Source: Cisco Systems
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
The following are listed in the CISA Known Exploited Vulnerabilities (KEV) Catalog:
CISA KEV CVE(s): CVE-2024-20353
CISA KEV URL: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Revision History: April 26 2024: Changed bulletin status to alert.
April 26 2024: Initial Release
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Cisco Adaptive Security Appliance and Firepower Threat Defense Software Web
Services Denial of Service Vulnerability
Priority: High
Advisory ID: cisco-sa-asaftd-websrvs-dos-X8gNucD2
First Published: 2024 April 24 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCwj10955
CVE Names: CVE-2024-20353
CWEs: CWE-835
Summary
o A vulnerability in the management and VPN web servers for Cisco Adaptive
Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD)
Software could allow an unauthenticated, remote attacker to cause the
device to reload unexpectedly, resulting in a denial of service (DoS)
condition.
This vulnerability is due to incomplete error checking when parsing an HTTP
header. An attacker could exploit this vulnerability by sending a crafted
HTTP request to a targeted web server on a device. A successful exploit
could allow the attacker to cause a DoS condition when the device reloads.
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-websrvs-dos-X8gNucD2
For more information on the vulnerability that is described in this
advisory, see Cisco Event Response: Attacks Against Cisco Firewall
Platforms .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco ASA Software and FTD Software if they have
one or more of the vulnerable configurations listed in the following two
tables.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine Whether an ASA or FTD Device Is Affected
To determine whether a device that is running Cisco ASA Software or FTD
Software is affected, use the show asp table socket | include SSL command
and look for an SSL listen socket on any TCP port. If a socket is present
in the output, the device should be considered vulnerable. The following
example shows the output for a Cisco ASA device with two SSL listen sockets
on TCP port 443 and TCP port 8443:
ciscoasa# show asp table socket | include SSL
SSL 00185038 LISTEN 172.16.0.250:443 0.0.0.0:*
SSL 00188638 LISTEN 10.0.0.250:8443 0.0.0.0:*
ASA Software Vulnerable Configuration
In the following table, the left column lists Cisco ASA Software features
that are potentially vulnerable. The right column indicates the basic
configuration for the feature from the show running-config CLI command, if
it can be determined. These features could cause the SSL listen sockets to
be enabled.
Cisco ASA Software Feature Possible Vulnerable Configuration
AnyConnect IKEv2 Remote Access (with crypto ikev2 enable [...]
client services) client-services port
Local Certificate Authority (CA) ^1 crypto ca server
no shutdown
Management Web Server Access (including http server enable
ASDM and CSM) ^2 http
webvpn
Mobile User Security (MUS) mus password
mus server enable port
mus
REST API ^3 rest-api image disk0:/rest-api
agent
SSL VPN webvpn
enable
1. In Cisco ASA Software Release 9.13 and later, Local CA is deprecated and
has been removed.
2. Management Web Server Access would only be vulnerable from an IP address
in the configured http command range.
3. REST API is vulnerable only from an IP address in the configured http
command range.
FTD Software Vulnerable Configuration
In the following table, the left column lists Cisco FTD Software features
that are potentially vulnerable. The right column indicates the basic
configuration for the feature from the show running-config CLI command, if
it can be determined. These features could cause the SSL listen sockets to
be enabled.
Cisco FTD Software Feature Possible Vulnerable Configuration
AnyConnect IKEv2 Remote Access (with crypto ikev2 enable [...]
client services) ^1,2 client-services port
AnyConnect SSL VPN ^1,2 webvpn
enable
HTTP server enabled ^3 http server enable
http
1. Remote access VPN features are enabled from Devices > VPN > Remote
Access in Cisco Firepower Management Center (FMC) Software or from Device >
Remote Access VPN in Cisco Firepower Device Manager (FDM).
2. Remote access VPN features are first supported as of Cisco FTD Software
Release 6.2.2.
3. The HTTP feature is enabled from Firepower Threat Defense Platform
Settings > HTTP in the Cisco FMC Console.
Products Confirmed Not Vulnerable
Only products and services 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 FMC
Software.
Workarounds
o There are no workarounds that address this vulnerability.
Fixed Software
o 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.html
Additionally, 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:
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 ASA Software or
6.6.7 for Cisco FTD Software.
5. Click Check .
[2 ] [ ] [Critical,High,Medium]
[Only this advisory ] [Cisco ASA Software]
[Any Platform ]
[ ] [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
Exploitation and Public Announcements
o Cisco has confirmed that this vulnerability has been exploited. Cisco
strongly recommends that customers upgrade to fixed software to resolve
this vulnerability. Customers are also strongly encouraged to monitor
system logs for indicators of undocumented configuration changes,
unscheduled reboots, and any anomalous credential activity.
Source
o Cisco would like to thank the following organizations for supporting this
investigation:
Australian Signals Directorate's Australian Cyber Security Centre
Canadian Centre for Cyber Security, a part of the Communications
Security Establishment
The UK's National Cyber Security Centre (NCSC)
U.S. Cybersecurity & Infrastructure Security Agency (CISA)
Cisco Security Vulnerability Policy
o 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.
Subscribe to Cisco Security Notifications
o Subscribe
Related to This Advisory
o Cisco Event Response: Attacks Against Cisco Firewall Platforms
URL
o https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-websrvs-dos-X8gNucD2
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2024-APR-24 |
+----------+---------------------------+----------+--------+--------------+
Legal Disclaimer
o THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND
OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT
OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES
THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information
or contain factual errors. The information in this document is intended for
end users of Cisco products.
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