CVE-2018-7167 in Node.js
Summary
by MITRE
Calling Buffer.fill() or Buffer.alloc() with some parameters can lead to a hang which could result in a Denial of Service. In order to address this vulnerability, the implementations of Buffer.alloc() and Buffer.fill() were updated so that they zero fill instead of hanging in these cases. All versions of Node.js 6.x (LTS "Boron"), 8.x (LTS "Carbon"), and 9.x are vulnerable. All versions of Node.js 10.x (Current) are NOT vulnerable.
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Analysis
by VulDB Data Team • 02/19/2020
The vulnerability described in CVE-2018-7167 represents a critical denial of service issue affecting specific versions of the Node.js runtime environment. This flaw manifests when developers invoke Buffer.fill() or Buffer.alloc() methods with certain parameter combinations that trigger an infinite loop condition within the underlying implementation. The vulnerability specifically impacts Node.js versions 6.x, 8.x, and 9.x, where the buffer allocation and filling mechanisms contain a logical error that causes the execution thread to hang indefinitely. The issue stems from improper parameter validation and handling within the core buffer management functions that are fundamental to Node.js applications. When these methods receive parameters that fall outside the expected validation criteria, the internal loop structures fail to terminate properly, leading to a complete system hang that can only be resolved through process termination or system reboot.
The technical root cause of this vulnerability aligns with CWE-835, which addresses the issue of infinite loops or iterations that can lead to denial of service conditions. The flaw occurs in the buffer management layer of Node.js where the allocation and filling functions do not properly validate input parameters before entering computationally expensive operations. This type of vulnerability falls under the ATT&CK technique T1499.004, which describes denial of service through resource exhaustion or system hanging conditions. The implementation error specifically affects the zero-filling behavior of buffer operations, where the system enters an infinite loop when attempting to fill buffers with certain invalid parameters. The vulnerability demonstrates poor defensive programming practices and inadequate input sanitization within the core Node.js runtime components that handle memory allocation and data manipulation tasks essential to application functionality.
The operational impact of CVE-2018-7167 extends beyond simple application hangs to encompass broader system stability and availability concerns. Applications running on vulnerable Node.js versions become susceptible to denial of service attacks that can be triggered by malicious input parameters, potentially allowing attackers to disrupt services or cause system-wide outages. The vulnerability affects all versions of Node.js 6.x, 8.x, and 9.x, making it particularly concerning for organizations maintaining legacy systems or those unable to immediately upgrade their runtime environments. The fix implemented by the Node.js team involved modifying the buffer allocation and filling implementations to ensure zero-filling behavior instead of entering hanging states, effectively breaking the infinite loop condition through proper parameter validation and termination criteria. This remediation approach aligns with security best practices for preventing denial of service conditions in runtime environments. Organizations running vulnerable versions must prioritize immediate upgrades to Node.js 10.x or later releases to mitigate this vulnerability, as the fix is not backported to the affected LTS versions. The vulnerability also highlights the importance of thorough testing of core runtime functions and the need for robust error handling in memory management operations to prevent similar issues in future implementations.