CVE-2018-9862 in runV
Summary
by MITRE
util.c in runV 1.0.0 for Docker mishandles a numeric username, which allows attackers to obtain root access by leveraging the presence of an initial numeric value on an /etc/passwd line, and then issuing a "docker exec" command with that value in the -u argument, a similar issue to CVE-2016-3697.
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Analysis
by VulDB Data Team • 02/27/2023
The vulnerability identified as CVE-2018-9862 affects runV version 1.0.0 within Docker environments and represents a critical privilege escalation flaw that exploits improper handling of numeric usernames in the util.c component. This issue demonstrates a classic case of insufficient input validation and sanitization that can be leveraged by malicious actors to gain elevated privileges within containerized environments. The vulnerability specifically targets the docker exec command functionality when used with the -u argument, creating a pathway for unauthorized users to obtain root access on the host system.
The technical flaw stems from how runV processes username specifications when executing commands within containers. When a numeric value is provided as a username in the -u argument of docker exec, the system fails to properly validate or sanitize this input before processing. The vulnerability exploits the fact that the system interprets initial numeric values in /etc/passwd entries as valid user identifiers without proper verification of the complete username format. This allows attackers to bypass normal user authentication mechanisms by crafting malicious username arguments that contain numeric values, effectively manipulating the system's user resolution process. The flaw is particularly dangerous because it operates at the container execution layer, where it can directly influence privilege escalation within the host system.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security isolation that containers are designed to provide. Attackers can leverage this vulnerability to execute arbitrary commands with root privileges on the host system, potentially leading to complete system compromise. The vulnerability is particularly concerning in multi-tenant environments where multiple users share the same Docker host, as it allows one user to escalate privileges and gain access to other users' containers or system resources. This issue also affects the broader container security ecosystem, as it demonstrates how seemingly minor input validation flaws can have catastrophic consequences for security boundaries. The vulnerability's similarity to CVE-2016-3697 indicates a persistent pattern in container runtime implementations where numeric username handling remains a weak point in privilege management systems.
Security mitigations for this vulnerability should focus on implementing robust input validation and sanitization mechanisms within the container runtime components. Organizations should immediately update their runV implementations to versions that properly handle numeric usernames and reject malformed input that could be exploited for privilege escalation. The fix should include proper validation of username formats, ensuring that numeric values are not accepted as valid usernames without proper context verification. Additionally, system administrators should implement strict access controls and monitoring around docker exec commands, particularly those involving the -u argument. This vulnerability aligns with CWE-20, which covers improper input validation, and maps to ATT&CK technique T1068, which involves exploiting privileges through local system manipulation. Organizations should also consider implementing container runtime security solutions that can detect and prevent suspicious username argument patterns, as well as establishing comprehensive logging and monitoring for docker exec operations to identify potential exploitation attempts.