CVE-2025-20136 Denial of service in Cisco Adaptive Security Appliance (ASA) Software
Remote attackers can cause Cisco ASA or FTD devices to reload via crafted DNS packets when NAT and DNS inspection are enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-20136?
CVE-2025-20136 is a high-severity denial of service vulnerability in Cisco Adaptive Security Appliance (ASA) Software, published on 14 Aug 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-835
Which versions are affected by CVE-2025-20136?
How do I fix CVE-2025-20136?
No fix has been published for CVE-2025-20136 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-20136 being exploited?
There is no known exploitation of CVE-2025-20136 in the wild and no public exploit code.
Sources
Also known as GHSA-w4q8-8r22-vpjc.