CVE-2018-7408 in npm
Summary
by MITRE
An issue was discovered in an npm 5.7.0 2018-02-21 pre-release (marked as "next: 5.7.0" and therefore automatically installed by an "npm upgrade -g npm" command, and also announced in the vendor's blog without mention of pre-release status). It might allow local users to bypass intended filesystem access restrictions because ownerships of /etc and /usr directories are being changed unexpectedly, related to a "correctMkdir" issue.
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Analysis
by VulDB Data Team • 02/08/2023
The vulnerability identified as CVE-2018-7408 represents a critical local privilege escalation issue affecting npm package manager versions including the pre-release 5.7.0 from February 21, 2018. This flaw emerged during the npm upgrade process where users executing "npm upgrade -g npm" would automatically install the "next: 5.7.0" version without explicit awareness of its pre-release status. The vulnerability stems from improper handling of directory ownership during filesystem operations, specifically within the "correctMkdir" function that manages directory creation and permission settings. This issue directly violates the principle of least privilege by allowing unauthorized modification of system-critical directories such as /etc and /usr, which are typically protected from arbitrary user modifications.
The technical implementation of this vulnerability involves the npm package manager's directory creation logic where the correctMkdir function fails to properly validate or maintain the ownership of system directories. When npm processes package installations or updates, it attempts to create directories with appropriate permissions, but due to the flawed ownership handling mechanism, it inadvertently changes the ownership of critical system directories. This occurs because the function does not properly check if the directories being created or modified are system-protected paths, leading to unexpected behavior where root ownership is overridden or improperly assigned. The vulnerability is particularly concerning because it operates at the filesystem level and can be exploited by local users without requiring network access or elevated privileges beyond basic user accounts.
The operational impact of CVE-2018-7408 extends beyond simple filesystem manipulation as it creates potential pathways for persistent system compromise and privilege escalation. An attacker exploiting this vulnerability could gain unauthorized access to system configuration files stored in /etc, potentially allowing for the modification of critical system settings, user authentication mechanisms, or service configurations. The change in ownership of /usr directories could enable attackers to modify system binaries or libraries, creating opportunities for code injection or backdoor installation. This vulnerability aligns with CWE-276, which addresses incorrect permissions for critical resources, and represents a significant deviation from expected system security boundaries. The attack surface is particularly wide because npm is widely used across development environments and system administration tasks, making this vulnerability exploitable across numerous deployment scenarios.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security hardening. The most direct approach involves upgrading to npm versions that have been patched to properly handle directory ownership and permissions, specifically avoiding the problematic pre-release versions. System administrators should implement strict version control policies for npm installations and ensure that pre-release packages are not automatically installed during routine updates. The vulnerability demonstrates the importance of proper input validation and privilege separation in system utilities, aligning with ATT&CK technique T1068 for privilege escalation and T1059 for command and scripting interpreter usage. Organizations should also implement monitoring for unexpected ownership changes in critical system directories and establish security awareness training to prevent users from inadvertently executing commands that could trigger this vulnerability. Additionally, implementing proper sandboxing or containerization of npm operations could provide an additional layer of protection against such filesystem-level attacks.