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CVE-2025-20136

Cisco Adaptive Security Appliance and Firepower Threat Defense Software Network Address Translation DNS Inspection Denial of Service Vulnerability

HIGH
8.6
CVSS Score
Published: August 14, 2025 at 04:28 PM UTC
Updated: June 17, 2026 at 08:40 AM UTC
2 products affected across 1 vendorAdaptive Security ApplianceFirepower Threat Defense

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Severity
HIGH8.6
Exploit prediction
EPSS 0.6%
SSVC
No known exploit

Description

A vulnerability in the function that performs IPv4 and IPv6 Network Address Translation (NAT) DNS inspection for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition.  This vulnerability is due to an infinite loop condition that occurs when a Cisco Secure ASA or Cisco Secure FTD device processes DNS packets with DNS inspection enabled and the device is configured for NAT44, NAT64, or NAT46. An attacker could exploit this vulnerability by sending crafted DNS packets that match a static NAT rule with DNS inspection enabled through an affected device. A successful exploit could allow the attacker to create an infinite loop and cause the device to reload, resulting in a DoS condition.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Adaptive Security Appliance· Cisco
60%
9.12.19.12.1.29.12.1.39.12.29.12.2.19.12.2.49.12.2.59.12.2.99.12.39.12.3.129.12.3.29.12.3.79.12.3.99.12.49.12.4.109.12.4.139.12.4.189.12.4.29.12.4.249.12.4.269.12.4.299.12.4.309.12.4.359.12.4.379.12.4.389.12.4.399.12.4.49.12.4.409.12.4.419.12.4.479.12.4.489.12.4.509.12.4.529.12.4.549.12.4.559.12.4.569.12.4.589.12.4.629.12.4.659.12.4.679.12.4.79.12.4.89.14.19.14.1.109.14.1.159.14.1.199.14.1.309.14.1.69.14.29.14.2.139.14.2.159.14.2.49.14.2.89.14.39.14.3.19.14.3.119.14.3.139.14.3.159.14.3.189.14.3.99.14.49.14.4.129.14.4.139.14.4.149.14.4.159.14.4.179.14.4.229.14.4.239.14.4.249.14.4.69.14.4.79.15.1.19.16.19.16.1.289.16.29.16.2.119.16.2.139.16.2.149.16.2.39.16.2.79.16.39.16.3.149.16.3.159.16.3.199.16.3.239.16.3.39.16.49.16.4.149.16.4.189.16.4.199.16.4.279.16.4.389.16.4.399.16.4.429.16.4.489.16.4.559.16.4.579.16.4.619.16.4.629.16.4.679.16.4.709.16.4.719.16.4.99.17.19.17.1.109.17.1.119.17.1.139.17.1.159.17.1.209.17.1.309.17.1.339.17.1.399.17.1.459.17.1.469.17.1.79.17.1.99.18.19.18.1.39.18.29.18.2.59.18.2.79.18.2.89.18.39.18.3.399.18.3.469.18.3.539.18.3.559.18.3.569.18.49.18.4.229.18.4.249.18.4.299.18.4.349.18.4.409.18.4.479.18.4.59.18.4.89.19.19.19.1.129.19.1.189.19.1.229.19.1.249.19.1.279.19.1.289.19.1.319.19.1.379.19.1.389.19.1.59.19.1.99.20.19.20.1.59.20.29.20.2.109.20.2.219.20.2.229.20.39.20.3.49.22.1.19.22.1.29.8.19.8.1.59.8.1.79.8.29.8.2.149.8.2.159.8.2.179.8.2.209.8.2.249.8.2.269.8.2.289.8.2.339.8.2.359.8.2.389.8.2.459.8.2.89.8.39.8.3.119.8.3.149.8.3.169.8.3.189.8.3.219.8.3.269.8.3.299.8.3.89.8.49.8.4.109.8.4.129.8.4.159.8.4.179.8.4.209.8.4.229.8.4.259.8.4.269.8.4.299.8.4.39.8.4.329.8.4.339.8.4.349.8.4.359.8.4.399.8.4.409.8.4.419.8.4.439.8.4.449.8.4.459.8.4.469.8.4.489.8.4.79.8.4.8
Firepower Threat Defense· Cisco
60%
6.2.36.2.3.16.2.3.106.2.3.116.2.3.126.2.3.136.2.3.146.2.3.156.2.3.166.2.3.176.2.3.186.2.3.26.2.3.36.2.3.46.2.3.56.2.3.66.2.3.76.2.3.86.2.3.96.4.06.4.0.16.4.0.106.4.0.116.4.0.126.4.0.136.4.0.146.4.0.156.4.0.166.4.0.176.4.0.186.4.0.26.4.0.36.4.0.46.4.0.56.4.0.66.4.0.76.4.0.86.4.0.96.6.06.6.0.16.6.16.6.36.6.46.6.56.6.5.16.6.5.26.6.76.6.7.16.6.7.27.0.07.0.0.17.0.17.0.1.17.0.27.0.2.17.0.37.0.47.0.57.0.67.0.6.17.0.6.27.0.6.37.1.07.1.0.17.1.0.27.1.0.37.2.07.2.0.17.2.17.2.27.2.37.2.47.2.4.17.2.57.2.5.17.2.5.27.2.67.2.77.2.87.2.8.17.2.97.3.07.3.17.3.1.17.3.1.27.4.07.4.17.4.1.17.4.27.4.2.17.6.0

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (1)

Source: [email protected]
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-nat-dns-dos-bqhynHTM

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.6HIGHcisco
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-835

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