CVE-2023-20080 is a denial of service (DoS) vulnerability in the Cisco IOS and IOS XE IPv6 DHCPv6 relay and server features. An unauthenticated, remote attacker could exploit this vulnerability by sending crafted DHCPv6 messages to affected devices. As a result, these devices could be forced to reload unexpectedly, causing service disruptions.

In this post, we will explore the details of CVE-2023-20080, along with code snippets and original references.

Vulnerability Details

Cisco IOS and IOS XE IPv6 DHCPv6 relay and server features contain a vulnerability arising from insufficient validation of data boundaries. An attacker exploiting this vulnerability could potentially cause a denial of service to the affected devices.

The Common Vulnerabilities and Exposures (CVE) project has assigned the identifier CVE-2023-20080 to this vulnerability.

Exploit Details

An attacker could exploit this vulnerability by sending specifically crafted DHCPv6 messages to affected devices. A successful exploit could force a device to unexpectedly reload, leading to a denial of service (DoS) condition. The attacker does not need to be authenticated and can launch the attack remotely.

Here is an example of a crafted DHCPv6 message that could be used in the attack

dhcpv6_server = attacker_IP
dhcpv6_message = """
\x00\xc\x01\x23\x00\xa\x01\x04\x00\x12\x05
\x12\x3a\x12\x34\x56\x78\x9a\xbc\xde\xf
"""

To understand more about crafted DHCPv6 messages and their role in the exploit, refer to the *RFC 3315: Dynamic Host Configuration Protocol for IPv6 (DHCPv6)* (link).

Cisco IOS XE Software: 3.1.S and later

For an extensive list of affected Cisco products, refer to the Cisco advisory (link).

Mitigation

To address this vulnerability, Cisco has released software updates. Users are advised to upgrade their Cisco IOS and IOS XE software to the latest available versions.

Conclusion

CVE-2023-20080 is a critical DoS vulnerability affecting the IPv6 DHCPv6 relay and server features of Cisco IOS and IOS XE software. An attacker could exploit this vulnerability to cause affected devices to reload unexpectedly, leading to service disruptions. Users are urged to apply software updates or implement suggested mitigations to protect their devices.

Original References

- Cisco Security Advisory
- CVE-2023-20080 - NVD
- RFC 3315: DHCPv6

Timeline

Published on: 03/23/2023 17:15:00 UTC
Last modified on: 03/31/2023 13:51:00 UTC