CVE-2020-2021: Palo Alto Networks PAN-OS Authentication Bypass Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 25 Mar 2022, 634 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 4.4%
EPSS score, percentile 91.2 of all scored records
- How severe?
- 10.0 Critical
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline 15 Apr 2022. Apply updates per vendor instructions.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- 8.0.*
- from 8.1 to before 8.1.15
- from 9.0 to before 9.0.9
- from 9.1 to before 9.1.3
Unaffected 7.1.*; from 8.1.15; from 9.0.9; from 9.1.3
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: 15 April 2022.
Solution (from the CVE record)
This issue is fixed in PAN-OS 8.1.15, PAN-OS 9.0.9, PAN-OS 9.1.3, and all later versions. Important: Ensure that the signing certificate for your SAML Identity Provider is configured as the 'Identity Provider Certificate' before you upgrade to a fixed version to ensure that your users can continue to authenticate successfully. Configuring the 'Identity Provider Certificate' is an essential part of a secure SAML authentication configuration. https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-admin/authentication/configure-saml-authentication Details of all actions required before and after upgrading PAN-OS are available in https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA14u0000008UXK. To eliminate unauthorized sessions on GlobalProtect portals and gateways, Prisma Access managed through Panorama, change the certificate used to encrypt and decrypt the Authentication Override cookie on the GlobalProtect portal and gateways using the Panorama or firewall web interface. Refer to this article for configuring Authentication override cookies: https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA14u0000008UXy Restarting firewalls and Panorama eliminates any unauthorized sessions on the web interface. To clear any unauthorized user sessions in Captive Portal take the following steps: Run the following command show user ip-user-mapping all type SSO For all the IPs returned, run these two commands to clear the users: clear user-cache-mp <above ips> clear user-cache <above ips> PAN-OS 8.0 is end-of-life (as of October 31, 2019) and is no longer covered by our Product Security Assurance policies. All Prisma Access services have been upgraded to resolve this issue and are no longer vulnerable. Prisma Access customers do not require any changes to SAML or IdP configurations.
Workaround (from the CVE record)
Using a different authentication method and disabling SAML authentication will completely mitigate the issue. Until an upgrade can be performed, applying both these mitigations (a) and (b) eliminates the configuration required for exposure to this vulnerability: (a) Ensure that the 'Identity Provider Certificate' is configured. Configuring the 'Identity Provider Certificate' is an essential part of a secure SAML authentication configuration. (b) If the identity provider (IdP) certificate is a certificate authority (CA) signed certificate, then ensure that the 'Validate Identity Provider Certificate' option is enabled in the SAML Identity Provider Server Profile. Many popular IdPs generate self-signed IdP certificates by default and the 'Validate Identity Provider Certificate' option cannot be enabled. Additional steps may be required to use a certificate signed by a CA. This certificate can be signed by an internal enterprise CA, the CA on the PAN-OS, or a public CA. Instructions to configure a CA-issued certificate on IdPs are available at https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA14u0000008UXP. Upgrading to a fixed version of PAN-OS software prevents any future configuration changes related to SAML that inadvertently expose protected services to attacks.
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Unaffected | 7.1.* |
| Affected | 8.0.* |
| Affected | from 8.1 to before 8.1.15 |
| Unaffected | from 8.1.15 |
| Affected | from 9.0 to before 9.0.9 |
| Unaffected | from 9.0.9 |
| Affected | from 9.1 to before 9.1.3 |
| Unaffected | from 9.1.3 |
Versions the record lists as unaffected: 7.1.*, 8.1.15, 9.0.9, 9.1.3.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
Palo Alto Networks PAN-OS contains a vulnerability in SAML which allows an attacker to bypass authentication.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2020-2021 to its Known Exploited Vulnerabilities (KEV) catalog on 25 Mar 2022.
- CISA marks it as known to be used in ransomware campaigns.
- The due date CISA sets for the required action is 15 Apr 2022.
- The CVE record was published on 29 Jun 2020, 634 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 10.0 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 4.4% (percentile 91.2), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
PAN-OS: Authentication Bypass in SAML Authentication
When Security Assertion Markup Language (SAML) authentication is enabled and the 'Validate Identity Provider Certificate' option is disabled (unchecked), improper verification of signatures in PAN-OS SAML authentication enables an unauthenticated network-based attacker to access protected resources. The attacker must have network access to the vulnerable server to exploit this vulnerability. This issue affects PAN-OS 9.1 versions earlier than PAN-OS 9.1.3; PAN-OS 9.0 versions earlier than PAN-OS 9.0.9; PAN-OS 8.1 versions earlier than PAN-OS 8.1.15, and all versions of PAN-OS 8.0 (EOL). This issue does not affect PAN-OS 7.1. This issue cannot be exploited if SAML is not used for authentication. This issue cannot be exploited if the 'Validate Identity Provider Certificate' option is enabled (checked) in the SAML Identity Provider Server Profile. Resources that can be protected by SAML-based single sign-on (SSO) authentication are: GlobalProtect Gateway, GlobalProtect Portal, GlobalProtect Clientless VPN, Authentication and Captive Portal, PAN-OS next-generation firewalls (PA-Series, VM-Series) and Panorama web interfaces, Prisma Access In the case of GlobalProtect Gateways, GlobalProtect Portal, Clientless VPN, Captive Portal, and Prisma Access, an unauthenticated attacker with network access to the affected servers can gain access to protected resources if allowed by configured authentication and Security policies. There is no impact on the integrity and availability of the gateway, portal or VPN server. An attacker cannot inspect or tamper with sessions of regular users. In the worst case, this is a critical severity vulnerability with a CVSS Base Score of 10.0 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N). In the case of PAN-OS and Panorama web interfaces, this issue allows an unauthenticated attacker with network access to the PAN-OS or Panorama web interfaces to log in as an administrator and perform administrative actions. In the worst-case scenario, this is a critical severity vulnerability with a CVSS Base Score of 10.0 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H). If the web interfaces are only accessible to a restricted management network, then the issue is lowered to a CVSS Base Score of 9.6 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H). Palo Alto Networks is not aware of any malicious attempts to exploit this vulnerability.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-347: Improper Verification of Cryptographic Signature
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 29 Jun 2020 | CVE record published |
| 25 Mar 2022 | Added to CISA KEV |
| 15 Apr 2022 | CISA due date for the required action |
| 21 Oct 2025 | CVE record last updated |
References
More exploited Palo Alto Networks vulnerabilities
- CVE-2026-0322: Palo Alto Networks PAN-OS Code Injection Vulnerability
- CVE-2026-0257: Palo Alto Networks PAN-OS Authentication Bypass Vulnerability
- CVE-2026-0300: Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
- CVE-2025-0111: Palo Alto Networks PAN-OS File Read Vulnerability
- CVE-2025-0108: Palo Alto Networks PAN-OS Authentication Bypass Vulnerability
- CVE-2024-3393: Palo Alto Networks PAN-OS Malicious DNS Packet Vulnerability