CVE-2025-20239 in IOS
Summary
by MITRE • 08/14/2025
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.
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Analysis
by VulDB Data Team • 07/31/2026
This vulnerability represents a critical denial of service weakness affecting Cisco's core networking and security infrastructure software platforms. The issue resides within the Internet Key Exchange Version 2 protocol implementation across multiple Cisco product lines including IOS Software, IOS XE Software, Secure Firewall Adaptive Security Appliance Software, and Secure Firewall Threat Defense Software. The flaw manifests as insufficient validation and processing of IKEv2 packets, creating a pathway for remote attackers to exploit the system without requiring authentication credentials. This vulnerability directly maps to CWE-400, which categorizes improper handling of input data leading to resource exhaustion conditions.
The technical exploitation mechanism involves sending specifically crafted IKEv2 packets to vulnerable devices, which triggers improper memory handling within the IKEv2 processing engine. In Cisco IOS and IOS XE environments, this flaw results in unexpected device reloads, effectively disrupting network connectivity and service availability. For Cisco ASA and FTD platforms, the impact is slightly different but equally disruptive, as attackers can partially deplete system memory resources, leading to instability that prevents establishment of new IKEv2 VPN sessions. This memory exhaustion creates a cascading effect that can severely impact network security operations and business continuity. The vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion.
The operational impact extends beyond simple service disruption to encompass broader network security implications. Organizations relying on these Cisco platforms for secure remote access and site-to-site connections face significant risk of unauthorized service interruption. The requirement for manual device reboot recovery adds to the operational burden and potential downtime. Network administrators must consider the vulnerability's potential for automated exploitation, as the lack of authentication requirements means attackers can initiate attacks at scale without detection. This vulnerability affects the fundamental security infrastructure of enterprise networks, potentially creating windows for more sophisticated attacks while simultaneously compromising the availability of critical security services. The memory leak characteristics of this flaw demonstrate a classic resource exhaustion attack pattern that can be amplified through repeated exploitation attempts.
Mitigation strategies should prioritize immediate patch deployment across all affected Cisco platforms, as the vulnerability exists in multiple software versions and product lines. Network segmentation and access control measures can help limit potential attack vectors by restricting direct access to vulnerable IKEv2 endpoints. Monitoring for unusual IKEv2 traffic patterns and implementing rate limiting on incoming packets can provide early detection capabilities. Organizations should also consider disabling IKEv2 functionality entirely if it is not essential for operations, though this may impact legitimate VPN connections. The implementation of intrusion detection systems capable of identifying crafted IKEv2 packets can provide additional defensive layers. Regular security assessments should verify that all network infrastructure components have been properly updated and that configuration changes have been implemented according to vendor security recommendations. This vulnerability underscores the importance of maintaining current security patches and implementing comprehensive network monitoring to detect and respond to exploitation attempts.