This is a vulnerability in a non-Atlassian Confluence dependency. Atlassian's application of this dependency presents a lower, non-critical assessed risk.

This Critical severity BASM (Broken Authentication & Session Management) vulnerability was introduced in versions 7.0.1, 7.1.0, 7.2.0, 7.3.1, 7.4.0, 7.5.0, 7.6.0, 7.7.2, 7.8.0, 7.9.0, 7.11.0, 7.12.0, 7.13.0, 7.14.0, 7.15.0, 7.16.0, 7.17.0, 7.18.0, 7.19.0, 7.20.0, 8.0.0, 8.1.0, 8.2.0, 8.3.0, 8.4.0, 8.5.0, 8.6.0, 8.7.1, 8.8.0, 8.9.0, 9.0.1, 9.1.0, 9.2.0, 9.3.1, 9.4.0, 9.5.1, 10.0.2, 10.1.0, and 10.2.0 of Confluence Data Center.

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 Confluence 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:

• Confluence Data Center 11.0: Upgrade to a release greater than or equal to 11.0.0
• Confluence Data Center 10.2: Upgrade to a release greater than or equal to 10.2.19
• Confluence Data Center 9.2: Upgrade to a release greater than or equal to 9.2.26

See the release notes (https://confluence.atlassian.com/doc/confluence-release-notes-327.html). You can download the
latest version of Confluence Data Center from the download center
(https://www.atlassian.com/software/confluence/download-archives).

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

Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause an IndexOutOfBoundsException and invoke select(ctx, null). This selects the default SslContext instead of the SNI-specific context. In deployments where per-SNI clientAuth=REQUIRE is the sole mutual TLS gate, the default SslContext uses clientAuth=NONE or clientAuth=OPTIONAL, and no application-layer certificate verification exists, an unauthenticated remote attacker can bypass the protected route's mutual TLS requirement. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.