This High severity CSRF (Cross-Site Request Forgery) vulnerability was introduced in versions 9.4.12, 10.2.0, 10.3.2, and 10.4.1 of Bitbucket Data Center.

This CSRF (Cross-Site Request Forgery) vulnerability, with a CVSS Score of 7.4 and a CVSS Vector of CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N allows an unauthenticated attacker to force a end user to execute unwanted actions on a web application in which they're currently authenticated 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 9.4.22
• Bitbucket Data Center 10.2: Upgrade to a release greater than or equal to 10.2.6
• Bitbucket Data Center 10.4: Upgrade to a release greater than or equal to 10.4.2

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: nanoid is a secure, URL-friendly, unique string ID generator for JavaScript. Prior to versions 3.3.12 and 5.1.11, the nanoid(size) function in index.js and index.cjs coerces the user-influenced size parameter to a signed 32-bit integer, allowing a value of 2147483648 to become -2147483648 and corrupt the process-wide CSPRNG poolOffset in fillPool(), which causes subsequent session tokens, CSRF tokens, API keys, and unique identifiers to become the deterministic string "uuuuuuuuuuuuuuuuuuuuu" until the process restarts. This issue is fixed in versions 3.3.12 and 5.1.11.