CVE-2021-41599 in GitHub
Summary
by MITRE • 02/18/2022
A remote code execution vulnerability was identified in GitHub Enterprise Server that could be exploited when building a GitHub Pages site. To exploit this vulnerability, an attacker would need permission to create and build a GitHub Pages site on the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.3 and was fixed in versions 3.0.21, 3.1.13, 3.2.5. This vulnerability was reported via the GitHub Bug Bounty program.
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Analysis
by VulDB Data Team • 02/19/2022
This vulnerability represents a critical remote code execution flaw in GitHub Enterprise Server that specifically impacts the GitHub Pages site building functionality. The security issue stems from improper input validation and sanitization during the site generation process, creating an avenue for malicious code injection that could be exploited by authenticated attackers with sufficient privileges. The vulnerability exists within the server-side processing pipeline that handles GitHub Pages site construction, where user-provided content and configuration files are parsed and executed without adequate security controls. This type of vulnerability falls under the CWE-74 category of Improper Neutralization of Special Elements in Output Used by a Downstream Component, specifically manifesting as a code injection vulnerability that allows arbitrary command execution.
The operational impact of CVE-2021-41599 is significant as it enables attackers with access to create and build GitHub Pages sites to execute arbitrary code on the server hosting the GitHub Enterprise instance. This represents a severe privilege escalation scenario where a relatively low-privilege user can potentially gain full control over the underlying server infrastructure. The vulnerability allows for arbitrary command execution through crafted input in the Pages site configuration files or content, which could be leveraged to establish persistent access, exfiltrate sensitive data, or disrupt services. Attackers could potentially use this vulnerability to deploy malicious payloads, escalate privileges within the system, or create backdoors for future access. The exploit requires only the ability to create and build Pages sites, which is often available to repository collaborators or users with appropriate permissions within the organization's GitHub Enterprise instance.
The fix for this vulnerability involved implementing proper input validation and sanitization mechanisms within the GitHub Pages site building process, ensuring that all user-provided content is properly escaped and validated before being processed by the server. This remediation aligns with security best practices outlined in the OWASP Top Ten and follows the principle of least privilege by restricting the execution environment of user-generated content. Organizations running affected versions of GitHub Enterprise Server should immediately upgrade to the patched versions 3.0.21, 3.1.13, or 3.2.5 to mitigate this risk. The vulnerability's discovery through the GitHub Bug Bounty program demonstrates the effectiveness of coordinated vulnerability disclosure programs in identifying and addressing security flaws before they can be widely exploited. Security teams should also implement monitoring for suspicious Pages site creation activities and review access controls to limit who can create and build Pages sites within their enterprise environments. This vulnerability highlights the importance of securing all components of web applications, particularly those involving user content processing and site generation capabilities, as they often represent attack surfaces that can be leveraged for more serious exploits.