CVE-2025-20222

High

Published: 14 August 2025

Published

14 August 2025

Modified

15 April 2026

KEV Added

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Patch

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CVSS Score 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS Score 0.0015 35.6th percentile

Risk Priority 17 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2025-20222 is a high-severity Classic Buffer Overflow (CWE-120) vulnerability in Cisco Secure Firewall (inferred from references). Its CVSS base score is 8.6 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 35.6th percentile by exploit likelihood (below the median); 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

What attackers do: exploitation maps to Application or System Exploitation (T1499.004). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Timely flaw remediation through vendor patches directly addresses the improper IPv6 packet processing vulnerability causing device reloads in Cisco ASA/FTD IPsec VPN RADIUS proxy.

SC-5 Denial-of-service Protection good match

prevent

Denial-of-service protection limits the impact of crafted IPv6 packets over IPsec VPN that trigger device reloads.

SI-10 Information Input Validation partial match

prevent

Information input validation on IPv6 packets mitigates the buffer copy without size check (CWE-120) in the RADIUS proxy feature.

MITRE ATT&CK Enterprise TechniquesAI

T1499.004 Application or System Exploitation Impact

Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.

attack.mitre.org →

Why these techniques?

Direct match to application/system exploitation causing DoS via crafted remote packets on a public-facing VPN service.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

A vulnerability in the RADIUS proxy feature for the IPsec VPN feature of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of…

service (DoS) condition. This vulnerability is due to improper processing of IPv6 packets. An attacker could exploit this vulnerability by sending IPv6 packets over an IPsec VPN connection to an affected device. A successful exploit could allow the attacker to trigger a reload of the device, resulting in a DoS condition.

Deeper analysisAI

CVE-2025-20222 is a denial-of-service (DoS) vulnerability in the RADIUS proxy feature for the IPsec VPN component of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software. The issue stems from improper processing of IPv6 packets, which could allow an unauthenticated, remote attacker to trigger a device reload. 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-120 (Buffer Copy without Checking Size of Input).

An unauthenticated, remote attacker can exploit this vulnerability by sending crafted IPv6 packets over an IPsec VPN connection to an affected device. Successful exploitation results in a reload of the device, causing a temporary DoS condition that disrupts network traffic processing until the device reboots.

The Cisco Security Advisory at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fp2k-IPsec-dos-tjwgdZCO details affected software versions, workarounds, and available patches for mitigation. Security practitioners should consult the advisory for specific upgrade recommendations and configuration guidance to address the vulnerability.