CISCO-SA-20190417-IOSXRACL

Vulnerability from csaf_cisco - Published: 2019-04-17 16:00 - Updated: 2019-04-17 16:00
Summary
Cisco ASR 9000 Series Aggregation Services Routers ACL Bypass Vulnerability
Notes
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.
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 ["#vp"] 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 ["https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html#fixes"], 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 ["https://www.cisco.com/go/psirt"], 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.
Vulnerability Policy: To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy ["https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html"]. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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.
Legal Disclaimer: 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.
CVE-2019-1686
5.8 (Medium)
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Affected products
Product Identifier Version Remediation
Cisco ASR 9000 Series Aggregation Services Routers
Cisco
 —
Vendor Fix fix
Workaround
Cisco IOS XR Software
Cisco
 —
Vendor Fix fix
Workaround
References
Acknowledgments
To clipboard 

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        "text": "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.\r\n\r\nThe 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.\r\n\r\nThere are workarounds that address this vulnerability.\r\n\r\n",
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        "text": "If the 5-tuple hash algorithm is used for load balancing, the device is not affected by the vulnerability described in this advisory.\r\n\r\nIf the 3-tuple hash algorithm is required, enabling ACL compression for the ACL on the interface is a workaround for this vulnerability.",
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        "title": "Fixed Software"
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        "text": "To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy [\"https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html\"]. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.",
        "title": "Vulnerability Policy"
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        "title": "Source"
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