Cisco ASR 9000 Series Aggregation Services Routers ACL Bypass Vulnerability

Medium

Advisory ID:

cisco-sa-20190417-iosxracl

First Published:

2019 April 17 16:00 GMT

Version 1.0:

Final

Workarounds:

Yes

Cisco Bug IDs:

CSCvm01102

CVE-2019-1686

CWE-284

CVSS Score:

Base 5.8Click Icon to Copy Verbose Score
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X

CVE-2019-1686

CWE-284

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Summary

• A vulnerability in the TCP flags inspection feature for access control lists (ACLs) on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to bypass protection offered by a configured ACL on an affected device.

  The vulnerability is due to incorrect processing of the ACL applied to an interface of an affected device when Cisco Express Forwarding load balancing using the 3-tuple hash algorithm is enabled. An attacker could exploit this vulnerability by sending traffic through an affected device that should otherwise be denied by the configured ACL. An exploit could allow the attacker to bypass protection offered by a configured ACL on the affected device.

  There are workarounds that address this vulnerability.

  This advisory is available at the following link:
  https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190417-iosxracl

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco ASR 9000 Series Aggregation Services Routers only when Cisco Express Forwarding load balancing using the 3-tuple hash algorithm is enabled. This capability is not enabled by default.

  For information about affected configurations and software releases, consult the Cisco bug ID(s) at the top of this advisory.

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

Workarounds

• If the 5-tuple hash algorithm is used for load balancing, the device is not affected by the vulnerability described in this advisory.

  If the 3-tuple hash algorithm is required, enabling ACL compression for the ACL on the interface is a workaround for this vulnerability.

Fixed Software

• For information about fixed software releases, consult the Cisco bug ID(s) at the top of this advisory.

  When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts 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.

Exploitation and Public Announcements

• 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.

Source

• This vulnerability was found during the resolution of a Cisco TAC support case.

Cisco Security Vulnerability Policy

• 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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URL

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190417-iosxracl

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2019-April-17

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Cisco Security Vulnerability Policy

• 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

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