This High severity MITM (Man-in-the-Middle) vulnerability was introduced in version 7.2.0 of Crowd Data Center.

This MITM (Man-in-the-Middle) vulnerability, with a CVSS Score of 8.7 and a CVSS Vector of CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N allows an unauthenticated attacker to potentially interdict connections to remote hosts, which has high impact to confidentiality, no impact to integrity, no impact to availability, and requires no user interaction.

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

• Crowd Data Center 7.2: Upgrade to a release greater than or equal to 7.2.4

See the release notes (https://confluence.atlassian.com/crowd/crowd-release-notes-199094.html). You can download the
latest version of Crowd Data Center from the download center
(https://www.atlassian.com/software/crowd/download-archive).

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

Netty (io.netty:netty-handler) versions from 4.2.0.Final through 4.2.16.Final and versions through 4.1.136.Final disable TLS hostname verification on the SslProvider.OPENSSL client path when a plain (non-extended) X509TrustManager is used and Unsafe-based trust-manager wrapping is unavailable (Java 25+). In this configuration the OpenSSL client does not perform hostname verification, allowing a man-in-the-middle attacker to present a certificate issued for a different hostname that is accepted without validation. Fixed in 4.2.17.Final and 4.1.137.Final.