CVE-2024-41956 in soft-serve
Summary
by MITRE • 08/02/2024
Soft Serve is a self-hostable Git server for the command line. Prior to 0.7.5, it is possible for a user who can commit files to a repository hosted by Soft Serve to execute arbitrary code via environment manipulation and Git. The issue is that Soft Serve passes all environment variables given by the client to git subprocesses. This includes environment variables that control program execution, such as LD_PRELOAD. This vulnerability is fixed in 0.7.5.
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Analysis
by VulDB Data Team • 08/02/2024
The vulnerability identified as CVE-2024-41956 affects Soft Serve, a command-line self-hostable Git server that enables users to manage repositories locally. This security flaw exists in versions prior to 0.7.5 and represents a critical code execution risk for systems utilizing this Git server implementation. The vulnerability stems from the application's improper handling of environment variables during Git subprocess execution, creating a pathway for malicious exploitation that could compromise the entire system.
The technical root cause of this vulnerability lies in Soft Serve's direct pass-through mechanism for client-provided environment variables to Git subprocesses without proper sanitization or validation. When a user with commit privileges to a repository attempts to manipulate environment variables during Git operations, the application forwards these variables unchanged to underlying Git processes. This behavior becomes particularly dangerous when environment variables like LD_PRELOAD are included, as these variables can control program loading and execution behavior. The LD_PRELOAD variable specifically allows attackers to inject malicious shared libraries that will be loaded before standard system libraries, enabling arbitrary code execution with the privileges of the Soft Serve process.
This vulnerability operates under the principles of environment variable manipulation and privilege escalation, aligning with CWE-250: Execution with Unnecessary Privileges and CWE-78: Improper Neutralization of Special Elements used in an OS Command. The operational impact of this vulnerability extends beyond simple code execution, as it allows attackers to potentially escalate privileges and gain full control over the Git server. The attack surface is particularly concerning because it requires only commit access to a repository, which many development teams grant to multiple contributors, making the vulnerability exploitable by a significant portion of users with legitimate access rights.
The attack vector follows a pattern where an attacker with commit privileges can craft a Git operation that includes malicious environment variables in their commit metadata. When the Soft Serve server processes these commits and executes Git commands, the environment variables are passed through to subprocesses, allowing the attacker's malicious code to execute. This scenario is particularly dangerous in multi-user environments where repository permissions are not strictly enforced, as it enables privilege escalation from repository contributor level to full system compromise. The vulnerability demonstrates a classic case of insufficient input validation and improper environment variable handling, where the application fails to distinguish between legitimate and malicious environment variable content.
Mitigation strategies for this vulnerability require immediate upgrade to Soft Serve version 0.7.5 or later, which implements proper environment variable sanitization. Organizations should also implement strict access controls and audit commit privileges to limit who can contribute to critical repositories. Additionally, system administrators should monitor for unusual Git operations and implement process monitoring to detect potential exploitation attempts. The fix addresses the core issue by filtering or sanitizing environment variables before passing them to Git subprocesses, preventing the injection of dangerous variables like LD_PRELOAD while maintaining functionality for legitimate use cases. This vulnerability highlights the importance of secure coding practices in subprocess execution and environment variable handling, particularly in applications that process user-supplied data and execute system commands. The remediation aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1548.001 for abuse of privileges, as it prevents both command execution and privilege escalation through environment manipulation.