CVE-2017-18026 in Redmine
Summary
by MITRE
Redmine before 3.2.9, 3.3.x before 3.3.6, and 3.4.x before 3.4.4 does not block the --config and --debugger flags to the Mercurial hg program, which allows remote attackers to execute arbitrary commands (through the Mercurial adapter) via vectors involving a branch whose name begins with a --config= or --debugger= substring, a related issue to CVE-2017-17536.
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Analysis
by VulDB Data Team • 01/20/2023
This vulnerability exists in Redmine versions prior to 3.2.9, 3.3.x prior to 3.3.6, and 3.4.x prior to 3.4.4, specifically within the Mercurial adapter functionality that enables integration with the Mercurial distributed version control system. The flaw stems from insufficient input validation and sanitization when processing branch names that contain Mercurial command-line flags, particularly the --config and --debugger parameters. Attackers can exploit this weakness by creating or manipulating branch names that begin with these specific flag prefixes, allowing them to inject arbitrary commands that get executed through the Mercurial hg program. This represents a command injection vulnerability that directly leverages the Mercurial adapter's handling of repository operations, making it particularly dangerous in environments where Redmine serves as a central project management platform with integrated version control capabilities.
The technical implementation of this vulnerability occurs through the Mercurial adapter's interaction with the hg command-line tool, where branch names are processed without proper sanitization of special characters or command flags. When a branch name begins with --config= or --debugger= substrings, these are interpreted by the Mercurial tool as command-line arguments rather than literal branch identifiers. This allows attackers to inject malicious parameters that can execute arbitrary code on the system running the Redmine application, potentially leading to full system compromise. The vulnerability is classified under CWE-78 as "Improper Neutralization of Special Elements used in an OS Command," which specifically addresses the risk of command injection when user-supplied data is passed to operating system commands without proper sanitization. The attack vector is particularly insidious because it exploits the legitimate functionality of Mercurial's command-line interface while masking malicious intent within seemingly normal branch naming conventions.
The operational impact of this vulnerability extends beyond simple code execution to encompass potential data breaches, system compromise, and unauthorized access to sensitive project information. Attackers can leverage this vulnerability to execute arbitrary commands with the privileges of the Redmine application user, which typically runs with sufficient permissions to access the underlying file system and potentially interact with other services. In enterprise environments where Redmine manages critical project data and integrates with various development workflows, this vulnerability could enable attackers to exfiltrate source code, modify project configurations, or establish persistent access points. The vulnerability affects not just the Mercurial integration but also represents a broader risk in applications that interface with external command-line tools, highlighting the importance of proper input validation and privilege separation in software development practices.
Organizations should immediately upgrade to Redmine versions 3.2.9, 3.3.6, or 3.4.4, respectively, to address this vulnerability and prevent exploitation. Additional mitigations include implementing strict branch naming policies that prohibit the use of special characters and command-line flags in branch names, disabling the Mercurial adapter functionality if not essential to operations, and monitoring for suspicious branch creation activities. Network-level protections such as firewalls and intrusion detection systems can help detect anomalous command execution patterns, while application-level logging should be enhanced to capture and analyze Mercurial command invocations. This vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter, specifically focusing on the execution of system commands through legitimate interfaces. Security teams should also consider implementing automated patch management processes to ensure timely remediation of similar vulnerabilities across all integrated systems and third-party applications that may be susceptible to similar command injection flaws in their external tool integrations.