CVE-2025-20142
Published: 12 March 2025
Summary
CVE-2025-20142 is a high-severity Improper Input Validation (CWE-20) vulnerability in Cisco Ios Xr. Its CVSS base score is 8.6 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 22.8% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly remediates the improper input validation flaw (CWE-20) by requiring timely application of vendor patches for affected Cisco IOS XR versions on ASR routers.
Implements denial-of-service protections such as rate limiting and traffic filtering to block crafted malformed IPv4 packets targeting ACL/QoS interfaces before they trigger line card resets.
Mandates validation of all information inputs, addressing the root cause of malformed IPv4 packet mishandling on affected line cards with ACL or QoS policies.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The CVE describes a remote unauthenticated DoS via crafted IPv4 packets exploiting improper input validation in a public-facing router's packet processing (ACL/QoS), directly enabling T1190 (Exploit Public-Facing Application) for the attack vector and T1499.004 (Application or System Exploitation) for causing process crash and service disruption.
NVD Description
A vulnerability in the IPv4 access control list (ACL) feature and quality of service (QoS) policy feature of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers, ASR 9902 Compact High-Performance Routers, and ASR 9903 Compact High-Performance…
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Routers could allow an unauthenticated, remote attacker to cause a line card to reset, resulting in a denial of service (DoS) condition. This vulnerability is due to the incorrect handling of malformed IPv4 packets that are received on line cards where the interface has either an IPv4 ACL or QoS policy applied. An attacker could exploit this vulnerability by sending crafted IPv4 packets through an affected device. A successful exploit could allow the attacker to cause network processor errors, resulting in a reset or shutdown of the network process. Traffic over that line card would be lost while the line card reloads. Note: This vulnerability has predominantly been observed in Layer 2 VPN (L2VPN) environments where an IPv4 ACL or QoS policy has been applied to the bridge virtual interface. Layer 3 configurations where the interface has either an IPv4 ACL or QoS policy applied are also affected, though the vulnerability has not been observed.
Deeper analysisAI
CVE-2025-20142 is a denial-of-service vulnerability in the IPv4 access control list (ACL) feature and quality of service (QoS) policy feature of Cisco IOS XR Software running on Cisco ASR 9000 Series Aggregation Services Routers, ASR 9902 Compact High-Performance Routers, and ASR 9903 Compact High-Performance Routers. The issue stems from improper handling of malformed IPv4 packets received on line cards where an interface has an IPv4 ACL or QoS policy applied. It has a CVSS v3.1 base score of 8.6 (AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H) and is associated with CWE-20 (Improper Input Validation).
An unauthenticated, remote attacker can exploit this vulnerability by sending crafted IPv4 packets through an affected device. A successful exploit triggers network processor errors, leading to a reset or shutdown of the network process on the targeted line card and a temporary loss of traffic over that line card during reload. The vulnerability has been predominantly observed in Layer 2 VPN (L2VPN) environments with an IPv4 ACL or QoS policy applied to the bridge virtual interface, though Layer 3 configurations with similar interface policies are also vulnerable despite lacking observed exploitation.
The Cisco Security Advisory at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ipv4uni-LfM3cfBu provides details on affected versions, workarounds, and fixed releases for mitigation. Security practitioners should consult this advisory for software upgrade guidance and configuration recommendations to address the issue.
Details
- CWE(s)