A Remote Code Execution (RCE) vulnerability was identified in GitHub Enterprise Server that allowed attackers to execute arbitrary code by exploiting the pre-receive hook functionality, potentially leading to privilege escalation and system compromise. The vulnerability involves using dynamically allocated ports that become temporarily available, such as during a hot patch upgrade. This means the vulnerability is only exploitable during specific operational conditions, which limits the attack window. Exploitation required either site administrator permissions to enable and configure pre-receive hooks or a user with permissions to modify repositories containing pre-receive hooks where this functionality was already enabled. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.18 and was fixed in versions 3.17.1, 3.16.4, 3.15.8, 3.14.13, 3.13.16. This vulnerability was reported via the GitHub Bug Bounty program.
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.