FG-IR-23-490: OpenSSH Terrapin attack (CVE-2023-48795)
CVE-2023-48795The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other products, allows remote attackers to bypass integrity checks such that some packets are omitted (from the extension negotiation message), and a client and server may consequently end up with a connection for which some security features have been downgraded or disabled, aka a Terrapin attack. This occurs because the SSH Binary Packet Protocol (BPP), implemented by these extensions, mishandles the handshake phase and mishandles use of sequence numbers. For example, there is an effective attack against SSH's use of ChaCha20-Poly1305 (and CBC with Encrypt-then-MAC). The bypass occurs in chacha20-poly1305@openssh.com and (if CBC is used) the -etm@openssh.com MAC algorithms.
Affected Software
Event History
Frequently Asked Questions
What is the severity of FG-IR-23-490?
The severity of FG-IR-23-490 is considered critical due to its potential to allow remote attackers to bypass integrity checks in the SSH transport protocol.
How do I fix FG-IR-23-490?
To fix FG-IR-23-490, update the affected Fortinet products to the recommended versions, such as upgrading FortiAnalyzer to version 7.4.3 or FortiMail to version 7.4.3.
Which products are affected by FG-IR-23-490?
Products affected by FG-IR-23-490 include various versions of FortiAnalyzer, FortiMail, FortiManager, and FortiWeb, among others.
What type of vulnerability is FG-IR-23-490?
FG-IR-23-490 is a vulnerability that involves SSH extension negotiation allowing for the omission of packets, enabling integrity check bypass.
Can FG-IR-23-490 lead to data compromise?
Yes, FG-IR-23-490 can potentially lead to data compromise as it allows attackers to manipulate SSH communications.