CVE-2023-48795 Impact of Terrapin SSH Attack
Description
The Terrapin attack allows an attacker with the ability to intercept SSH traffic on affected Palo Alto Networks products (through machine-in-the-middle or MitM attacks) to downgrade connection security and force the usage of less secure client authentication algorithms when an administrator or user connects to the product.
This issue does not impact the SSH server component of PAN-OS software configured to exclusively use strong cipher algorithms or configured to operate in FIPS-CC mode, which removes support for the impacted algorithms.
When using the PAN-OS SSH client to connect to an SSH server that supports the CHACHA20-POLY1305 algorithm or any Encrypt-then-MAC algorithms, the traffic is susceptible to this attack.
This issue affects Prisma SD-WAN ION devices.
Additional information and technical details about the attack can be found at https://terrapin-attack.com.
Product Status
| Versions | Affected | Unaffected |
|---|---|---|
| PAN-OS 11.1 | < 11.1.3 | >= 11.1.3 (ETA: beginning of May) |
| PAN-OS 11.0 | < 11.0.7 | >= 11.0.7 (ETA: end of July) |
| PAN-OS 10.2 | < 10.2.11 | >= 10.2.11 (ETA: end of June) |
| PAN-OS 10.1 | All | TBD |
| PAN-OS 9.1 | All | TBD |
| PAN-OS 9.0 | All | None |
| Prisma SD-WAN ION 6.2 | < 6.2.4 | >= 6.2.4 (ETA: end of June) |
| Prisma SD-WAN ION 6.1 | < 6.1.8 | >= 6.1.8 |
| Prisma SD-WAN ION 5.6 | < 5.6.19 | >= 5.6.19 (ETA: end of July) |
Required Configuration for Exposure
The SSH server in PAN-OS software configured with support for the CHACHA20-POLY1305 algorithm or any Encrypt-then-MAC algorithms (ciphers with -etm in the name) enables the Terrapin Attack and is impacted by this issue.
Severity: MEDIUM
CVSSv4.0 Base Score: 6 (CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/AU:N/R:A/V:D/RE:L/U:Amber)
Exploitation Status
Palo Alto Networks is not aware of any malicious exploitation of this issue.
Weakness Type
CWE-354 Improper Validation of Integrity Check Value
Solution
PAN-OS customers can resolve this issue by configuring the in-use SSH profile to contain at least one cipher and at least one MAC algorithm, which removes support for CHACHA20-POLY1305 and all Encrypt-then-MAC algorithms available (ciphers with -etm in the name) in PAN-OS software. Guidance on how to configure strong ciphers and algorithms can be found on the following pages:
- https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA14u0000004OOQCA2
To validate that the affected ciphers and algorithms are no longer enabled, please see the guidance at: https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA14u000000kF2eCAE
This issue is completely resolved by following the recommended best practices for deploying PAN-OS (https://docs.paloaltonetworks.com/best-practices/10-1/administrative-access-best-practices/administrative-access-best-practices/deploy-administrative-access-best-practices). No additional PAN-OS fixes are planned in maintenance releases at this time.
The PAN-OS SSH client will be fixed in an upcoming release of PAN-OS 9.1 and PAN-OS 10.1, PAN-OS 10.2.11, PAN-OS 11.0.7, PAN-OS 11.1.3, and all later PAN-OS versions. This advisory will be updated with release estimates as they become available.
This issue is fixed in Prisma SD-WAN ION 6.1.8, and will be fixed in Prisma SD-WAN ION 5.6.19, Prisma SD-WAN ION 6.2.4, and all later Prisma SD-WAN ION versions.
Workarounds and Mitigations
If using the SSH client provided with PAN-OS to connect from the firewall to an external SSH server, ensure that the SSH server does not support the CHACHA20-POLY1305 algorithm or any Encrypt-then-MAC algorithms.