CVE-2020-8252 in libuv
Summary
by MITRE
The implementation of realpath in libuv < 10.22.1, < 12.18.4, and < 14.9.0 used within Node.js incorrectly determined the buffer size which can result in a buffer overflow if the resolved path is longer than 256 bytes.
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Analysis
by VulDB Data Team • 05/18/2025
The vulnerability identified as CVE-2020-8252 represents a critical buffer overflow flaw within the libuv library implementation of the realpath function. This issue affects multiple versions of libuv including those below 10.22.1, 12.18.4, and 14.9.0, with widespread implications for Node.js applications that depend on these library versions. The vulnerability stems from an incorrect buffer size determination during path resolution operations, creating a scenario where applications can experience memory corruption when processing file paths exceeding 256 bytes in length. This flaw directly impacts the core file system operations that Node.js applications rely upon for path resolution and validation.
The technical implementation flaw manifests in how libuv handles the allocation and management of buffers during realpath operations. When the system attempts to resolve a symbolic link or canonicalize a file path, the library allocates a fixed-size buffer that is insufficient for handling extended paths. This buffer overflow occurs because the implementation fails to properly account for the potential length of the resolved path, particularly when dealing with deeply nested directories or long symbolic link chains. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, representing a classic memory safety issue that can lead to arbitrary code execution or system instability. The flaw is particularly dangerous because it occurs in a fundamental system call that is frequently invoked during normal application operation.
From an operational perspective, this vulnerability poses significant risks to Node.js applications running on affected versions of libuv. Attackers can exploit this buffer overflow by crafting malicious file paths that exceed the 256-byte threshold, potentially leading to denial of service conditions, arbitrary code execution, or information disclosure. The impact extends beyond individual applications to affect entire systems where Node.js services are deployed, particularly in environments where file system operations are frequent or where applications process user-provided paths without proper validation. The vulnerability aligns with ATT&CK technique T1059.006 for execution through Node.js, and can be leveraged as part of broader exploitation chains targeting application servers and web services. Organizations using affected versions of Node.js may experience system crashes, data corruption, or unauthorized access if this vulnerability is successfully exploited.
Mitigation strategies for CVE-2020-8252 primarily involve upgrading to patched versions of libuv and Node.js, with the specific recommended versions being libuv 10.22.1, 12.18.4, and 14.9.0 or later. System administrators should conduct comprehensive inventory checks to identify all affected Node.js installations and implement patch management procedures to ensure timely remediation. Additionally, organizations should consider implementing input validation measures to limit path lengths and sanitize file system operations, particularly when processing external or user-provided data. Network segmentation and application firewalls can provide additional defense-in-depth measures, while monitoring systems should be configured to detect anomalous file system access patterns that might indicate exploitation attempts. The vulnerability underscores the importance of maintaining up-to-date dependencies and implementing robust security practices for software supply chain management, particularly for core libraries that form the foundation of application security.