What’s Vulnerable › Vulnerabilities

CVE-2021-34696: Cisco ASR 900 and ASR 920 Series Aggregation Services Routers Access Control List Bypass Vulnerability

• Severity: medium (CVSS 5.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-09-23 · updated 2026-06-17
• Weakness: CWE-284

Description

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. This vulnerability is due to incorrect programming of hardware when an ACL is configured using a method other than the configuration CLI. An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to bypass an ACL on the affected device.

Affected products

• Cisco IOS XE: through 17.3.2

References

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr900acl-UeEyCxkv
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr900acl-UeEyCxkv

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