CVE-2017-18365 in GitHub
Summary
by MITRE
The Management Console in GitHub Enterprise 2.8.x before 2.8.7 has a deserialization issue that allows unauthenticated remote attackers to execute arbitrary code. This occurs because the enterprise session secret is always the same, and can be found in the product's source code. By sending a crafted cookie signed with this secret, one can call Marshal.load with arbitrary data, which is a problem because the Marshal data format allows Ruby objects.
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Analysis
by VulDB Data Team • 08/08/2023
The vulnerability identified as CVE-2017-18365 represents a critical deserialization flaw within the Management Console of GitHub Enterprise 2.8.x versions prior to 2.8.7. This issue stems from a fundamental security weakness in how the system handles session management and object serialization. The root cause lies in the hardcoded session secret that remains consistent across all installations, making it discoverable within the product's source code. This predictable secret creates an exploitable condition that bypasses authentication requirements entirely.
The technical exploitation of this vulnerability occurs through a carefully crafted cookie that leverages the known session secret to generate a valid signature. When the Management Console processes this malicious cookie, it invokes Marshal.load with arbitrary data provided by the attacker. The Ruby Marshal data format, while useful for serialization purposes, becomes dangerous when processing untrusted input because it can execute arbitrary code during the deserialization process. This behavior aligns with CWE-502, which specifically addresses deserialization of untrusted data as a security risk.
The operational impact of this vulnerability is severe and far-reaching, as it enables unauthenticated remote code execution on affected GitHub Enterprise installations. Attackers can leverage this flaw to gain complete control over the management console without requiring any credentials or authentication. This provides attackers with access to sensitive administrative functions and potentially allows them to compromise the entire GitHub Enterprise instance. The vulnerability affects organizations that rely on GitHub Enterprise for their code repository management and collaboration needs, creating significant risk for code integrity and data security.
Organizations should immediately upgrade to GitHub Enterprise 2.8.7 or later versions to remediate this vulnerability. The fix addresses the hardcoded session secret issue by implementing proper randomization of session secrets during installation. Additionally, administrators should conduct thorough security assessments of their GitHub Enterprise deployments to ensure no unauthorized access has occurred. The vulnerability demonstrates the critical importance of proper session management and the dangers of hardcoded cryptographic secrets in web applications. This issue also relates to ATT&CK technique T1059.007 for Ruby, which covers the execution of malicious code through Ruby deserialization attacks. Security teams should implement network monitoring to detect suspicious cookie patterns and consider implementing web application firewalls to block known malicious payloads targeting this specific vulnerability.