CVE-2022-0028: Palo Alto Networks PAN-OS Reflected Amplification Denial-of-Service Vulnerability

1. Summary 

2. About CVE-2022-0028

2.1 Introduction 

PAN‑OS is the software that runs all Palo Alto Networks next-generation firewalls. 

2.2 Summary 

A PAN-OS URL filtering policy misconfiguration could allow a network-based attacker to conduct reflected and amplified TCP denial-of-service (RDoS) attacks. The DoS attack would appear to originate from a Palo Alto Networks PA-Series (hardware), VM-Series (virtual) and CN-Series (container) firewall against an attacker-specified target. To be misused by an external attacker, the firewall configuration must have a URL filtering profile with one or more blocked categories assigned to a source zone that has an external facing interface. This configuration is not typical for URL filtering and, if set, is likely unintended by the administrator.

This issue is applicable to PA-Series (hardware), VM-Series (virtual), and CN-Series (container) firewalls only when all three of the following conditions are true:

1. The security policy on the firewall that allows traffic to pass from Zone A to Zone B includes a URL filtering profile with one or more blocked categories; 
2. Packet-based attack protection is not enabled in a Zone Protection profile for Zone A including both (Packet Based Attack Protection > TCP Drop > TCP Syn With Data) and (Packet Based Attack Protection > TCP Drop > Strip TCP Options > TCP Fast Open);
3. Flood protection through SYN cookies is not enabled in a Zone Protection profile for Zone A (Flood Protection > SYN > Action > SYN Cookie) with an activation threshold of 0 connections.

If exploited, this issue would not impact the confidentiality, integrity, or availability of Palo Alto products. How+ever, the resulting denial-of-service (DoS) attack may help obfuscate the identity of the attacker and implicate the firewall as the source of the attack.

CVE-2022-0028 was added to CISA’s Known Exploited Vulnerabilities Catalog on August 22, 2022, and Palo Alto Networks is also aware of an attempted reflected denial-of-service (RDoS) attack using the vulnerability. This attempted attack took advantage of susceptible firewalls from multiple vendors, including Palo Alto Networks.

3. Affected Versions 

8.1 ≤ Palo Alto PAN-OS < 8.1.23-h1   

9.0 ≤ Palo Alto PAN-OS < 9.0.16-h3 

9.1 ≤ Palo Alto PAN-OS < 9.1.14-h4 

10.0 ≤ Palo Alto PAN-OS < 10.0.11-h1 

10.1 ≤ Palo Alto PAN-OS < 10.1.6-h6 

10.2 ≤ Palo Alto PAN-OS < 10.2.2-h2 

4. Solutions

4.1 Remediation Solutions

Palo Alto Networks has released software updates for all affected PAN-OS versions. Users should apply updates per vendor instructions.

4.2 Workarounds

If you have a URL filtering policy with one or more blocked categories assigned to a security rule with a source zone that has an external facing interface, removing this configuration will prevent this issue from being exploited by remote attackers to conduct reflected DoS.

To prevent denial-of-service (DoS) attacks resulting from this issue from all sources, you can configure your Palo Alto Networks firewalls by enabling one of two zone protection mitigations on all Security zones with an assigned Security policy that includes a URL filtering profile: 

1. Packet-based attack protection including both (Packet Based Attack Protection > TCP Drop > TCP SYN with Data) and (Packet Based Attack Protection > TCP Drop > Strip TCP Options > TCP Fast Open); 

OR 

2. Flood protection (Flood Protection > SYN > Action > SYN Cookie) with an activation threshold of 0 connections. 

NOTES:

• It is not necessary nor advantageous to apply both the attack and flood protections. 
• (Palo Alto Networks Aporeto software only) You should not enable either of these protections if using Aporeto software; instead, wait for and install a fixed version of PAN-OS software. 

Packet-Based Attack Protection Workaround (Recommended)

Follow the technical documentation to configure packet-based attack protection options for all defined Security zones with URL filtering enabled in the Security profile for that zone: https://docs.paloaltonetworks.com/pan-os/10-2/pan-os-admin/zone-protection-and-dos-protection/configure-zone-protection-to-increase-network-security/configure-packet-based-attack-protection 

The packet-based attack protection workaround will prevent the firewall from establishing TCP sessions in impacted zones when the TCP SYN packet contains data in the three-way handshake for a TCP session. Please note that this workaround may disrupt applications that use TCP Fast Open in the zone. 

Flood Protection (Alternate) Workaround 

If you instead decide to enable the flood protection workaround, first make sure you understand how enabling SYN cookies will change traffic flow in the impacted zones: https://docs.paloaltonetworks.com/pan-os/10-2/pan-os-admin/zone-protection-and-dos-protection/zone-defense/zone-protection-profiles/flood-protection 

5. Reference 

https://nvd.nist.gov/vuln/detail/CVE-2022-0028#range-8260226 

https://security.paloaltonetworks.com/CVE-2022-0028 

6. Learn More 

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