CVE-2017-1000116 in Mercurial
Summary
by MITRE
Mercurial prior to 4.3 did not adequately sanitize hostnames passed to ssh, leading to possible shell-injection attacks.
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Analysis
by VulDB Data Team • 12/30/2022
The vulnerability identified as CVE-2017-1000116 affects Mercurial version 4.3 and earlier, representing a critical security flaw in the distributed version control system's handling of SSH connections. This issue stems from insufficient sanitization of hostnames when establishing secure shell connections, creating a pathway for malicious actors to execute arbitrary commands on affected systems. The flaw specifically targets the SSH transport mechanism used by Mercurial to communicate with remote repositories, making it particularly dangerous for organizations that rely on SSH-based workflows for code management and collaboration.
The technical implementation of this vulnerability occurs within Mercurial's SSH connection handling code where hostname parameters are not properly validated or escaped before being passed to underlying shell commands. When users specify repository URLs containing specially crafted hostnames, the system fails to sanitize these inputs, allowing attackers to inject shell metacharacters and commands that get executed with the privileges of the user running Mercurial. This represents a classic shell injection vulnerability that can be exploited through various attack vectors including malformed repository URLs, maliciously configured SSH hosts, or manipulated configuration files that specify remote endpoints.
The operational impact of this vulnerability extends beyond simple command execution, as it can lead to complete system compromise when attackers leverage the shell injection to escalate privileges, exfiltrate sensitive data, or establish persistent backdoors within the affected environment. Organizations using Mercurial for code repositories, especially those with multiple developers accessing remote systems through SSH, face significant risk exposure. The vulnerability affects both local and remote repository operations, making it particularly dangerous in enterprise environments where Mercurial is used for continuous integration workflows, automated deployments, and collaborative development processes. Attackers can exploit this flaw without requiring authentication to the target repository, making it an attractive vector for automated attacks against exposed Mercurial installations.
Mitigation strategies for CVE-2017-1000116 primarily involve upgrading to Mercurial version 4.3 or later, which includes proper hostname sanitization and input validation mechanisms. System administrators should also implement network-level controls such as firewall rules that restrict SSH access to trusted networks, and employ SSH key-based authentication to minimize the attack surface. The vulnerability aligns with CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, and maps to ATT&CK technique T1059.001 for command and script injection. Organizations should also consider implementing repository access controls, monitoring for suspicious repository operations, and conducting regular security audits of their version control infrastructure to identify and remediate similar vulnerabilities in other tools and systems within their environment.