Invite tokens have Insufficient entropy in GHES Management Console

Summary

An insufficient entropy vulnerability was identified in GitHub Enterprise Server (GHES) that allowed an attacker to brute force a user invitation to the GHES Management Console. To exploit this vulnerability, an attacker would need knowledge that a user invitation was pending. This vulnerability affected all versions of GitHub Enterprise Server since 3.8 and was fixed in version 3.8.12, 3.9.7, 3.10.4, and 3.11.1. This vulnerability was reported via the GitHub Bug Bounty program.

Invitation tokens generated by the Github Management Console had low entropy allowing an attacker to iterate over the low number of potential combinations in order to take over a pending user account creation. To exploit this vulnerability, an attacker would need knowledge that a user invitation was pending.