This High severity BASM (Broken Authentication & Session Management) vulnerability was introduced in versions 9.0.1, 9.1.0, 9.2.0, 9.3.0, 9.4.0, 9.5.0, 9.6.0, 10.0.0, 10.1.1, 10.2.0, and 10.3.0 of Bitbucket Data Center.

This BASM (Broken Authentication & Session Management) vulnerability, with a CVSS Score of 8.1 and a CVSS Vector of CVSS:3.1/AV:N/AC:L/PR:L/UI:N/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 no user interaction.

Atlassian recommends that Bitbucket 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:

• Bitbucket Data Center 9.4: Upgrade to a release greater than or equal to 9.4.7

• Bitbucket Data Center 10.2: Upgrade to a release greater than or equal to 10.2.5

• Bitbucket Data Center 10.3: Upgrade to a release greater than or equal to 10.3.2

See the release notes (https://confluence.atlassian.com/bitbucketserver/release-notes). You can download the latest version of Bitbucket Data Center from the download center (https://www.atlassian.com/software/bitbucket/download-archives).

The National Vulnerability Database provides the following description for this vulnerability: SubjectDnX509PrincipalExtractor does not correctly handle certain malformed X.509 certificate CN values, which can lead to reading the wrong value for the username. In a carefully crafted certificate, this can lead to an attacker impersonating another user.

Affected versions:
Spring Security 5.7.0 through 5.7.24; 5.8.0 through 5.8.26; 6.3.0 through 6.3.17; 6.4.0 through 6.4.17; 6.5.0 through 6.5.10.