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Cisco Bug: CSCvh81737 - Cisco Adaptive Security Appliance Denial of Service Vulnerability

Last Modified

Aug 07, 2019

Products (1)

  • Cisco ASA 5500-X Series Firewalls

Known Affected Releases

9.7

Description (partial)

Symptom:
UPDATED 2/5/2018: After further investigation, Cisco has identified additional attack vectors and features that are 
affected by this vulnerability. In addition it was also found that the original fix was incomplete so new fixed code 
versions are now available. Please see the Fixed Software section for more information.

A vulnerability in the XML parser of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, 
remote attacker to cause a reload of the affected system or to remotely execute code. It was also possible that  the ASA 
could stop processing incoming Virtual Private Network (VPN) authentication requests due to a low memory condition.

The vulnerability is due to an issue with allocating and freeing memory when processing a malicious XML payload. An 
attacker could exploit this vulnerability by sending a crafted XML packet to a vulnerable interface on an affected system. 
An exploit could allow the attacker to execute arbitrary code and obtain full control of the system, cause a reload of the 
affected device or stop processing of incoming VPN authentication requests.

To be vulnerable the ASA must have Secure Socket Layer (SSL) services or IKEv2 Remote Access VPN services enabled
on an interface. The risk of the vulnerability being exploited also depends on the accessibility of the interface to the attacker.
For a comprehensive list of vulnerable ASA features please refer to the table in the Vulnerable Products section.

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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180129-asa1

Conditions:
Please refer to the Security Advisory.
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Bug Details Include

  • Full Description (including symptoms, conditions and workarounds)
  • Status
  • Severity
  • Known Fixed Releases
  • Related Community Discussions
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