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CVE-2020-2021
KEV ransomwarelargeSAML Authentication Bypass in Palo Alto Networks PAN-OS
CISA: Palo Alto Networks PAN-OS Authentication Bypass Vulnerability
CVSS 3.1
10.0 critical
EPSS
4%p91
Published
()
KEV added
AI analysis
CVE-2020-2021 is an improper signature-verification flaw (CWE-347) in PAN-OS SAML authentication that lets an unauthenticated network-based attacker bypass identity verification when SAML is enabled and the 'Validate Identity Provider Certificate' option is left unchecked. An attacker with network access to a vulnerable GlobalProtect gateway or portal, GlobalProtect Clientless VPN, Captive Portal, or Prisma Access can gain access to protected resources permitted by the configured authentication and security policies, without affecting session integrity or availability for regular users. If SAML is used to protect the PAN-OS or Panorama web interfaces, the attacker can log in as an administrator and perform administrative actions, making this a worst-case CVSS 10.0 (critical) issue. Affected deployments run PAN-OS 9.1 before 9.1.3, 9.0 before 9.0.9, 8.1 before 8.1.15, or any 8.0 release (end-of-life); PAN-OS 7.1 is not affected, and the flaw cannot be exploited where SAML is unused or certificate validation is enabled. The vendor reported no malicious exploitation at disclosure, but the flaw has since been added to CISA's Known Exploited Vulnerabilities catalog (March 2022) with known ransomware use, and headlines tie it to foreign espionage and APT activity chaining VPN flaws.
What to do: Upgrade to PAN-OS 9.1.3, 9.0.9, or 8.1.15 or later as applicable, and migrate off EOL PAN-OS 8.0; PAN-OS 7.1 requires no action. As an immediate mitigation, enable (check) the 'Validate Identity Provider Certificate' option in the SAML Identity Provider Server Profile. Restrict the PAN-OS and Panorama web interfaces to a trusted management network and audit whether SAML is used for GlobalProtect, Captive Portal, Prisma Access, or administrator authentication to confirm exposure.
Affected
| Palo Alto Networks PAN-OS | 9.1 versions earlier than 9.1.3; 9.0 versions earlier than 9.0.9; 8.1 versions earlier than 8.1.15; all PAN-OS 8.0 versions (EOL); PAN-OS 7.1 not affected |
Estimated exposure
largetens of thousands of internet-exposed PAN-OS firewalls, gateways and management interfaces, of an installed base of hundreds of thousands — Public internet scans at the time of disclosure showed on the order of 70,000+ GlobalProtect portals and comparable numbers of PAN-OS web interfaces reachable from the internet, but only the subset that uses SAML authentication with…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
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.
CISA Known Exploited Vulnerability
- Affected
- Palo Alto Networks PAN-OS
- Required action
- Apply updates per vendor instructions.
- Due date
- Ransomware use
- Known
- Vendors
- paloaltonetworks
- Products
- pan-os
- Weakness
- CWE-347
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
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