A broken authentication vulnerability has been identified in Jira Service Management Server and Data Center versions after 5.3.0. Atlassian Support have published a security advisory to inform users of this vulnerability, which they have rated as critical severity, with a CVSS base score of 9.4. Versions of Jira Service Management Server and Data Center affected by this vulnerability include 5.3.0, 5.3.1, 5.3.2, 5.4.0, 5.4.1, and 5.5.0. Fixed versions have been released by Atlassian, so users can upgrade to one of these to patch their systems. Fixed versions include version 5.3.3, 5.4.2, 5.5.1, and 5.6.0 or later. Atlassian have stated that Atlassian Cloud sites accessed via atlassian.net domains are not affected by this flaw. 

This authentication vulnerability CVE-2023-22501 can be exploited by an attacker in order to gain access to an instance of Jira Service Management by impersonating another user. The severity of the attack is conditional to the settings enabled and permissions granted on the Jira Service Management account that the attacker impersonates. If the attacker can impersonate a user with write access to a User Directory, and there is outgoing email enabled on the Jira Service Management instance, then the attacker can access signup tokens sent to new users who have not yet logged on for the first time. The attacker can gain access to these tokens by either being included on the Jira issues or requests with the target users, or the attacker can be forwarded the emails from Jira containing the ‘View Request’ link.  

Atlassian have warned that bot accounts are the most vulnerable to this form of attack, as well as external customer accounts where any user can create their own account, and in instances with single sign-on enabled. Administrators should upgrade any Jira Service Management instances with these account types in particular as soon as possible. The fixed versions for Jira Service Management Server and Data Center can be found online by visiting the Atlassian Download Center. If an immediate upgrade is not possible, an official temporary workaround to mitigate this vulnerability is to manually upgrade the affected JAR file. This workaround is version-specific, so the correct servicedesk-variable-substitution-plugin JAR file must first be identified for the affected version of Jira before this can be implemented. A list of JAR files for affected Jira Service Management versions can be found in the Mitigation section of the Atlassian security advisory for this vulnerability, along with instructions on how to perform this manual upgrade.