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

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.