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AUSCERT External Security Bulletin Redistribution
ESB-2022.3992.2
CVE-2022-0028 PAN-OS: Reflected Amplification
Denial-of-Service (DoS) Vulnerability in URL Filtering
15 August 2022
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AusCERT Security Bulletin Summary
---------------------------------
Product: PAN-OS
Publisher: Palo Alto Networks
Operating System: Network Appliance
Resolution: Patch/Upgrade
CVE Names: CVE-2022-0028
Original Bulletin:
https://securityadvisories.paloaltonetworks.com/CVE-2022-0028
Comment: CVSS (Max): 8.6 CVE-2022-0028 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
CVSS Source: Palo Alto Networks
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Revision History: August 15 2022: Vendor updated the Product Status and Solution details
August 11 2022: Initial Release
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Palo Alto Networks Security Advisories / CVE-2022-0028
CVE-2022-0028 PAN-OS: Reflected Amplification Denial-of-Service (DoS)
Vulnerability in URL Filtering
047910
Severity 8.6 . HIGH
Attack Vector NETWORK
Scope CHANGED
Attack Complexity LOW
Confidentiality Impact NONE
Privileges Required NONE
Integrity Impact NONE
User Interaction NONE
Availability Impact HIGH
NVD JSON
Published 2022-08-10
Updated 2022-08-12
Reference PAN-192999
Discovered externally
Description
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
security rule with a source zone that has an external facing network interface.
This configuration is not typical for URL filtering and, if set, is likely
unintended by the administrator.
If exploited, this issue would not impact the confidentiality, integrity, or
availability of our products. However, 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.
We have taken prompt action to address this issue in our PAN-OS software. All
software updates for this issue are expected to be released no later than the
week of August 15, 2022. This issue does not impact Panorama M-Series or
Panorama virtual appliances.
This issue has been resolved for all Cloud NGFW and Prisma Access customers and
no additional action is required from them.
Product Status
Versions Affected Unaffected
Cloud NGFW None All
PAN-OS 10.2 < 10.2.2-h2 >= 10.2.2-h2 (ETA: week of August 15, 2022)
PAN-OS 10.1 < 10.1.6-h6 >= 10.1.6-h6
PAN-OS 10.0 < 10.0.11-h1 >= 10.0.11-h1 (ETA: week of August 15, 2022)
PAN-OS 9.1 < 9.1.14-h4 >= 9.1.14-h4 (ETA: week of August 15, 2022)
PAN-OS 9.0 < 9.0.16-h3 >= 9.0.16-h3 (ETA: week of August 15, 2022)
PAN-OS 8.1 < 8.1.23-h1 >= 8.1.23-h1 (ETA: August 15, 2022)
Prisma Access 3.1 None All
Prisma Access 3.0 None All
Prisma Access 2.2 None All
Prisma Access 2.1 None All
Required Configuration for Exposure
The firewall configuration must have a URL filtering profile with one or more
blocked categories assigned to a security rule with a source zone that has an
external facing interface for this issue to be misused by an external attacker.
This configuration is not typical for URL filtering and 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;
AND
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);
AND
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.
Severity:HIGH
CVSSv3.1 Base Score:8.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
Exploitation Status
Palo Alto Networks recently learned that an attempted reflected
denial-of-service (RDoS) attack was identified by a service provider. This
attempted attack took advantage of susceptible firewalls from multiple vendors,
including Palo Alto Networks. We immediately started to root cause and
remediate this issue.
Exploitation of this issue does not impact the confidentiality, integrity, or
availability of our products.
Weakness Type
CWE-406 Insufficient Control of Network Message Volume (Network Amplification)
Solution
We identified workarounds to prevent the denial-of-service (DoS) attacks that
result from this issue in certain Palo Alto Networks firewalls, with this
policy configuration.
This issue is fixed in PAN-OS 10.1.6-h6 and all later PAN-OS versions for
PA-Series, VM-Series and CN-Series firewalls. We intend to fix this issue in
the following PAN-OS software releases: PAN-OS 8.1.23-h1 (ETA: August 15,
2022), PAN-OS 9.0.16-h3 (ETA: week of August 15, 2022), PAN-OS 9.1.14-h4 (ETA:
week of August 15, 2022), PAN-OS 10.0.11-h1 (ETA: week of August 15, 2022), and
PAN-OS 10.2.2-h2 (ETA: week of August 15, 2022).
We expect to release all PAN-OS software updates for this issue no later than
the week of August 15, 2022.
Workarounds and Mitigations
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
Acknowledgments
This issue was found by the Shadowserver Foundation and responsibly reported to
Palo Alto Networks by Excellium-Services S.A. CSIRT, CERT-XLM.
Frequently Asked Questions
Q. How is this a high severity vulnerability if it does not impact the security
of the firewall?
Though exploitation of this issue does not impact the confidentiality,
integrity, or availability of your firewall or appliance, the resulting
denial-of-service (DoS) attack can potentially result in a loss of
availability for the attacker-specified target if that target lacks
sufficient DoS protection.
Q. Why is this considered a misconfiguration or unintended configuration?
Palo Alto Networks URL filtering solution allows you to monitor and control
the sites users can access, to prevent phishing attacks by controlling the
sites to which users can submit valid corporate credentials, and to enforce
safe search for search engines like Google and Bing.
The URL filtering policies are intended to be triggered when a user inside
a protected network requests to visit dangerous or disallowed sites on the
Internet in traffic destined to the Internet. Such requests are blocked and
the browser displays a "Web Page Blocked" message.
Such URL filtering is not meant to be used in the other direction for
traffic coming from the Internet to the protected network. URL filtering in
that direction offers no benefits. Hence any firewall configuration that is
doing this is likely unintentional and considered a misconfiguration.
Q. Why is this fixed with software updates if this is due to a
misconfiguration?
The misconfiguration exposes the vulnerability which enables remote network
based attackers to conduct reflected denial of service (RDoS) attacks. The
PAN-OS fixes resolve this vulnerability eliminating this RDoS risk for the
misconfigured firewalls and from internal threats.
Q. How do I know if my firewall(s) are being misused for conducting DoS
attacks?
An abnormal increase in URL Filtering Logs with a block action that has a
large number of retries by the same set of external source IP addresses is
an indicator of this misuse.
Timeline
2022-08-12 An update to the acknowledgements section of the advisory.
2022-08-10 PAN-OS 10.1.6-h6 fixed version is now available. Updated ETA for
PAN-OS 8.1.23-h1. Clarified URL filtering assignment language.
2022-08-10 Initial publication
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(C) 2022 Palo Alto Networks, Inc. All rights reserved.
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