CVE-2025-20239 Denial of service in Cisco Adaptive Security Appliance (ASA) Software
Unauthenticated remote attackers can cause denial of service via crafted IKEv2 packets, requiring Cisco network device administrators to apply patches.
- 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-2025-20239?
CVE-2025-20239 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 Internet Key Exchange Version 2 (IKEv2) feature of Cisco IOS Software, IOS XE Software, Secure Firewall Adaptive Security Appliance (ASA) Software, and Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a memory leak, resulting in a denial of service (DoS) condition. This vulnerability is due to a lack of proper processing of IKEv2 packets. An attacker could exploit this vulnerability by sending crafted IKEv2 packets to an affected device. In the case of Cisco IOS and IOS XE Software, a successful exploit could allow the attacker to cause the device to reload unexpectedly. In the case of Cisco ASA and FTD Software, a successful exploit could allow the attacker to partially exhaust system memory, causing system instability such as being unable to establish new IKEv2 VPN sessions. A manual reboot of the device is required to recover from this condition.
Weakness: CWE-401
Which versions are affected by CVE-2025-20239?
How do I fix CVE-2025-20239?
No fix has been published for CVE-2025-20239 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-2025-20239 being exploited?
There is no known exploitation of CVE-2025-20239 in the wild and no public exploit code.
Sources
Also known as GHSA-vfr5-7cjj-f96c.