This Critical severity BASM (Broken Authentication & Session Management) vulnerability was introduced in version 4.9.0 of Crucible Server.

This BASM (Broken Authentication & Session Management) vulnerability, with a CVSS Score of 9.1 and a CVSS Vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N allows an unauthenticated attacker to expose assets in your environment susceptible to exploitation, which has high impact to confidentiality, high impact to integrity, no impact to availability, and requires no user interaction.

Atlassian recommends that Crucible Server customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions:

• Crucible Server 4.9: Upgrade to a release greater than or equal to 4.9.15

See the release notes (https://confluence.atlassian.com/crucible/crucible-releases-298977378.html). You can download the
latest version of Crucible Server from the download center
(https://www.atlassian.com/software/crucible/download-archives).

The National Vulnerability Database provides the following description for this vulnerability:

Authentication bypass in sshd-core in Apache MINA SSHD versions 2.0.0 to 2.19.0 and 3.0.0-M1 to 3.0.0-M5 for a certain (presumed rare) way to implement an SSH server.

Apache MINA SSHD is a Java library for client- and server-side SSH. In the server part of the library, a mechanism to perform "asynchronous authentication" exists. A server implemented with Apache MINA SSHD must contain explicit code to make use of this feature. The implementation of this feature was flawed and could potentially lead to skipping checking the signature in public-key or hostbased authentication, or returning a wrong result.

Users are recommended to upgrade to Apache MINA SSHD 2.20.0 or 3.0.0-M6, which fix the logic error and which additionally forbid the use of this "asynchronous authentication" mechanism with the public-key or hostbased authentication schemes: if used, the SSH session will be closed and the server will log an entry indicating that asynchronous authentication may be used only with password or keyboard-interactive authentication.