Cisco ASA and Firepower Threat Defense Allow for Security Bypass

Fortify Security Team
Nov 3, 2021

A vulnerability has been discovered in Cisco Adaptive Security Appliance and Firepower Threat Defense, which could allow attackers to bypass security mechanisms on the system. Successful exploitation of this vulnerability could allow an unauthenticated remote attacker to bypass security mechanisms on the targeted host.

THREAT INTELLIGENCE: There are currently no reports of this vulnerability being exploited in the wild.

SYSTEMS AFFECTED:

  • Cisco Adaptive Security Appliance (ASA) Software 9.7 and earlier
  • Cisco Adaptive Security Appliance (ASA) Software prior to 9.8.4.40
  • Cisco Adaptive Security Appliance (ASA) Software prior to 9.12.4.25
  • Cisco Adaptive Security Appliance (ASA) Software prior to 9.14.3.1
  • Cisco Adaptive Security Appliance (ASA) Software prior to 9.15.1.17
  • Cisco Adaptive Security Appliance (ASA) Software prior to 9.16.1.28
  • Cisco Adaptive Security Appliance (ASA) Software 9.9, 9.10, and 9.13
  • Cisco Firepower Threat Defense (FTD) Software 6.3 and earlier
  • Cisco Firepower Threat Defense (FTD) Software prior to 6.4.0.13
  • Cisco Firepower Threat Defense (FTD) Software prior to 6.6.5
  • Cisco Firepower Threat Defense (FTD) Software prior to 6.7.0.3
  • Cisco Firepower Threat Defense (FTD) Software prior to 7.0.1
  • Cisco Firepower Threat Defense (FTD) Software prior to 7.0.1
  • Cisco Firepower Threat Defense (FTD) Software 6.5

RISK:
Government:

  • Large and medium government entities: High
  • Small government entities: High

Businesses:

  • Large and medium business entities: High
  • Small business entities: High

Home users: Low

TECHNICAL SUMMARY:

A vulnerability has been discovered in Cisco Adaptive Security Appliance and Firepower Threat Defense, which could allow attackers to bypass security mechanisms on the system. The vulnerability is the result of a design error in the identity-based firewall (IDFW) rule processing feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software, which could allow an unauthenticated, remote attacker to bypass security protections (CVE-2021- 34787). Attackers may be able to exploit this issue by sending a specially crafted network request to an affected device.

RECOMMENDATIONS:

We recommend the following actions be taken:

  • Install the update provided by Cisco immediately after appropriate testing.
  • Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
  • Remind users not to visit websites or follow links provided by unknown or untrusted sources.
  • Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from un-trusted sources.
  • Apply the Principle of Least Privilege to all systems and services.

REFERENCES:
Cisco:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-rule-bypass-ejjOgQEY

CVE:
https://www.cve.org/CVERecord?id=CVE-2021-34787

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