This High severity BASM (Broken Authentication & Session Management) vulnerability was introduced in version 4.9.7 of Crucible Server.

This BASM (Broken Authentication & Session Management) vulnerability, with a CVSS Score of 7.3 and a CVSS Vector of CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N allows an authenticated attacker to perform actions as another user which has high impact to confidentiality, high impact to integrity, no impact to availability, and requires 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 Data Center and Server 4.9: Upgrade to a release greater than or equal to 4.9.13

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: Improper certificate validation in Apache MINA SSHD (server-side). Apache MINA SSHD is a Java library for client-side and server-side SSH.

Server-side OpenSSH user certificate validation during user authentication in an Apache MINA SSHD server did not check for the unsupported force-command or verify-required options that could be embedded in the certificate, nor did it validate these options. As a result it was possible that a user could authenticate with such a certificate that included a force-command option but still was able to execute other commands. What other command exactly would be available to the user depends on the implementation of the server.

This issue is fixed in Apache MINA SSHD 2.19.0 and 3.0.0-M5. Applications are advised to upgrade to these versions.

The fix rejects OpenSSH user certificates that include these options, since Apache MINA SSHD implements neither force-command nor sk-*-cert-v01@openssh.com user certificates (which are the only ones for which verify-required would make sense).