CVE-2023-23764 in GitHub
Summary
by MITRE • 07/28/2023
An incorrect comparison vulnerability was identified in GitHub Enterprise Server that allowed commit smuggling by displaying an incorrect diff within the GitHub pull request UI. To do so, an attacker would need write access to the repository. This vulnerability affected GitHub Enterprise Server versions 3.7.0 and above and was fixed in versions 3.7.9, 3.8.2, and 3.9.1. This vulnerability was reported via the GitHub Bug Bounty program.
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Analysis
by VulDB Data Team • 08/20/2023
The vulnerability CVE-2023-23764 represents a critical flaw in GitHub Enterprise Server's pull request user interface that enables commit smuggling through manipulated diff displays. This issue stems from an incorrect comparison mechanism that fails to properly validate or display changes in code modifications, creating a deceptive interface that misrepresents the actual content being merged. The vulnerability specifically targets the visual representation of differences between commits, allowing attackers to obscure malicious changes within legitimate code modifications.
The technical implementation of this flaw occurs within the GitHub Enterprise Server's code comparison engine, which processes and displays diff information for pull requests. When an attacker with write access manipulates commit data, the system's comparison algorithm incorrectly evaluates the differences between modified files, resulting in a misleading visual representation that hides malicious code changes. This vulnerability operates at the application layer and directly impacts the integrity of the code review process through improper input validation and comparison logic. The flaw falls under the category of CWE-254, which encompasses security weaknesses related to improper comparison operations, and specifically aligns with CWE-754, concerning the improper handling of comparison operations that could lead to security implications.
The operational impact of this vulnerability extends beyond simple code manipulation, as it fundamentally undermines the trust model that code review processes rely upon. An attacker with write privileges can exploit this weakness to introduce malicious code that appears benign within the pull request interface, potentially bypassing security controls and automated scanning systems. The vulnerability creates a window of opportunity for attackers to execute commit smuggling attacks, where harmful modifications are embedded within legitimate code changes without detection. This capability directly violates the principle of least privilege and can lead to privilege escalation or persistent backdoors within the codebase. The affected versions 3.7.0 and above indicate that this vulnerability has been present for multiple release cycles, potentially allowing attackers to maintain undetected access for extended periods.
Security practitioners must understand that this vulnerability represents a sophisticated attack vector that targets the integrity of source code management systems. The fix implemented in versions 3.7.9, 3.8.2, and 3.9.1 addresses the root cause by correcting the comparison algorithm and implementing more robust validation of diff outputs. Organizations should prioritize immediate patching of affected systems and conduct thorough audits of recent commits to identify potential exploitation. The vulnerability's discovery through the GitHub Bug Bounty program demonstrates the importance of coordinated disclosure and community-driven security research in identifying critical flaws within widely-used enterprise platforms. This incident underscores the necessity for continuous security testing of user interface components and the validation of comparison operations in version control systems. The attack surface for this vulnerability includes not only the direct code modification capabilities but also the broader implications for code review workflows and security automation that depend on accurate diff representations.