CVE-2025-8447 is a high-severity authorization bypass vulnerability affecting GitHub Enterprise Server versions prior to 3.18. The flaw arises from improper access control related to the compare/diff functionality between repositories. Specifically, users with access to any repository on the server could exploit this vulnerability to retrieve limited code content from other private repositories to which they should not have access. The exploitation requires the attacker to know the exact name of the target private repository and at least one branch, tag, or commit SHA to trigger the diff operation. This vulnerability is categorized under CWE-639, which involves authorization bypass through user-controlled keys. The vulnerability was addressed in GitHub Enterprise Server versions 3.14.17, 3.15.12, 3.16.8, and 3.17.5. The CVSS 4.0 base score is 7.0, reflecting a high severity level, with network attack vector, low attack complexity, partial privileges required, no user interaction, and high impact on confidentiality. No known exploits are reported in the wild as of the publication date. The vulnerability was responsibly disclosed via the GitHub Bug Bounty program. This flaw could allow unauthorized disclosure of sensitive source code, potentially exposing intellectual property, security mechanisms, or credentials embedded in code, which could be leveraged for further attacks or competitive disadvantage.

For European organizations using GitHub Enterprise Server internally or as part of their development infrastructure, this vulnerability poses a significant risk to the confidentiality of proprietary and sensitive codebases. Unauthorized access to private repositories could lead to intellectual property theft, exposure of security-sensitive code (such as cryptographic implementations or authentication logic), and leakage of credentials or API keys embedded in code. This could facilitate further attacks such as supply chain compromises, insider threats, or targeted cyber espionage. Given the widespread adoption of GitHub Enterprise Server by enterprises, including many in Europe, the impact could extend to critical sectors such as finance, manufacturing, technology, and government agencies. The breach of code confidentiality could also undermine compliance with data protection regulations like GDPR if personal data or security controls are exposed indirectly through code. Although no active exploitation is reported, the ease of exploitation (low complexity, no user interaction) and network accessibility increase the urgency for patching.

European organizations should immediately verify their GitHub Enterprise Server versions and upgrade to the fixed releases (3.14.17, 3.15.12, 3.16.8, 3.17.5 or later). In addition to patching, organizations should audit repository access controls to ensure the principle of least privilege is enforced, limiting repository access strictly to necessary users. Monitoring and logging of repository compare/diff operations should be enhanced to detect anomalous or unauthorized attempts to access private repositories. Organizations should also review and rotate any credentials or secrets stored in repositories that might have been exposed. Implementing network segmentation to restrict access to GitHub Enterprise Server management interfaces and repositories can reduce exposure. Finally, conducting internal security awareness and training for developers and administrators about secure repository management and the risks of unauthorized data access is recommended.