This High severity Race condition vulnerability was introduced in version 10.3.0 of Bitbucket Data Center.

This Race condition vulnerability, with a CVSS Score of 7 and a CVSS Vector of CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H allows an authenticated attacker to modify code sequences in which exclusive access to shared resources is operating concurrently which has high impact to confidentiality, high impact to integrity, high 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 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: file.copy operations in GruntJS are vulnerable to a TOCTOU race condition leading to arbitrary file write in GitHub repository gruntjs/grunt prior to 1.5.3. This vulnerability is capable of arbitrary file writes which can lead to local privilege escalation to the GruntJS user if a lower-privileged user has write access to both source and destination directories as the lower-privileged user can create a symlink to the GruntJS user's .bashrc file or replace /etc/shadow file if the GruntJS user is root.