CVE-2021-1243: Cisco IOS XR Software SNMP Management Plane Protection ACL Bypass Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-02-04 · updated 2026-06-17
Weakness: CWE-284

Description

A vulnerability in the Local Packet Transport Services (LPTS) programming of the SNMP with the management plane protection feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to allow connections despite the management plane protection that is configured to deny access to the SNMP server of an affected device. This vulnerability is due to incorrect LPTS programming when using SNMP with management plane protection. An attacker could exploit this vulnerability by connecting to an affected device using SNMP. A successful exploit could allow the attacker to connect to the device on the configured SNMP ports. Valid credentials are required to execute any of the SNMP requests.

Affected products

Cisco IOS XR Software: from 6.1.1 (excl.) before 6.6.4; from 7.0.0 before 7.0.2; 6.7.1, 7.0.11, 7.1.0, 7.2.0 — fixed in 6.6.4, 7.0.2

How to fix

Upgrade to a fixed version: Cisco IOS XR Software 6.6.4, 7.0.2. Check the vendor advisory for mitigations.

References

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