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CVE-2025-20191: Denial of Service Vulnerability in Cisco Security Features

Overview

The vulnerability, identified as CVE-2025-20191, affects the Switch Integrated Security Features (SISF) of multiple Cisco software products. This vulnerability is crucial as it allows an unauthenticated attacker to potentially cause a denial of service (DoS) condition on the affected device, compromising system stability and potentially leading to data leakage.

Vulnerability Summary

CVE ID: CVE-2025-20191
Severity: High (7.4)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Denial of Service, potential system compromise and data leakage

Affected Products

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Product | Affected Versions

Cisco IOS Software | All vulnerable versions
Cisco IOS XE Software | All vulnerable versions
Cisco NX-OS Software | All vulnerable versions
Cisco WLC AireOS Software | All vulnerable versions

How the Exploit Works

The vulnerability stems from the incorrect handling of DHCPv6 packets. An attacker can exploit this by sending a crafted DHCPv6 packet to the affected device. If successfully exploited, the device reloads, resulting in a Denial of Service condition.

Conceptual Example Code

Below is a conceptual example of how an attacker might craft a malicious DHCPv6 packet to exploit this vulnerability. Note that this is a simplified representation and real-world attacks would require more complex code:

import scapy.all as scapy
# Create a malicious DHCPv6 packet
packet = scapy.IPv6()/scapy.UDP(dport=547)/scapy.DHCP6_Reply()
# Add malicious data to the packet
packet[scapy.DHCP6_Reply].options.append(scapy.DHCP6OptUnknown(optcode=666, optlen=666, optdata="...malicious data..."))
# Send the packet to the target device
scapy.send(packet, iface="eth0")

Please note that the actual malicious data would need to be specifically crafted to exploit the vulnerability in the target device, which is not covered in this simplification.

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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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