QID 317063

Date Published: 2021-11-15

QID 317063: Cisco ASR 900 and ASR 920 Series Aggregation Services Routers (ASR) Access Control List Bypass Vulnerability (cisco-sa-asr900acl-UeEyCxkv)

A vulnerability in the access control list (ACL) programming of Cisco ASR 900 and
ASR 920 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to bypass a configured ACL.

Affected Products
Cisco products if they were running a vulnerable release of Cisco IOS XE Software and had an IPv4 ACL configured:
ASR 900 Series Aggregation Services Routers with Route Switch Processors (RSPs) 1, 2, or 3
ASR 920 Series Aggregation Services Routers
Note: This vulnerability has not been found in ACLs that are manually configured using the CLI.
However, there is no mechanism to determine whether an ACL has been correctly programmed on a device.
Potential Detection as cannot confirm RSPs 1,2 or 3 and how is IPV4 ACL configured.

QID Detection Logic (Authenticated):
The check matches Cisco IOS XE version retrieved via Unix Auth using "show version" command.
QID Detection Logic (Unauthenticated):
The check matches Cisco IOS XE version retrieved via SNMP or TCP/IP Fingerprint or NTP or Telnet.

A successful exploit could allow the attacker to bypass an ACL on the affected device.

  • CVSS V3 rated as Medium - 5.8 severity.
  • CVSS V2 rated as Medium - 5 severity.
    • Solution

    Customers are advised to refer to cisco-sa-asr900acl-UeEyCxkv for more information.

    Vendor References

    CVEs related to QID 317063

    CVE-2021-34696 |
    Software Advisories
    Advisory ID Software Component Link
    cisco-sa-asr900acl-UeEyCxkv URL Logo tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr900acl-UeEyCxkv
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