CVE-2018-3745 in atob
Summary
by MITRE
atob 2.0.3 and earlier allocates uninitialized Buffers when number is passed in input on Node.js 4.x and below.
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Analysis
by VulDB Data Team • 02/09/2020
The vulnerability identified as CVE-2018-3745 affects the atob module version 2.0.3 and earlier in Node.js environments running version 4.x and below. This issue represents a classic buffer management flaw that stems from improper handling of input data types within the base64 decoding implementation. The vulnerability specifically manifests when numeric values are passed as input to the atob function, leading to the allocation of uninitialized memory buffers that contain sensitive data from previous operations.
The technical root cause of this vulnerability lies in the improper type checking and memory allocation logic within the atob implementation. When a numeric value is passed to the function instead of a string, the underlying code fails to properly validate the input type and instead proceeds with memory allocation based on the numeric value's magnitude. This creates a scenario where the system allocates memory buffers without proper initialization, potentially exposing previously allocated memory contents to the current operation. This behavior directly aligns with CWE-122, which describes improper restriction of operations within a memory buffer, and specifically relates to buffer overflow conditions that can occur due to inadequate input validation and memory management.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates potential attack vectors for memory corruption exploits. An attacker who can control the input to the atob function could potentially manipulate the memory allocation process to read sensitive data from adjacent memory locations, including credentials, session tokens, or other confidential information stored in the application's memory space. The vulnerability is particularly concerning in Node.js 4.x environments where memory management practices may be less robust compared to newer versions, and where the uninitialized buffer allocation could provide attackers with access to previously used memory segments.
Mitigation strategies for this vulnerability require immediate attention from system administrators and developers. The primary recommendation involves upgrading to atob module versions 2.0.4 and later, which contain proper input validation and memory allocation handling. Additionally, implementing strict input validation at application level can prevent numeric values from reaching the vulnerable function, using type checking mechanisms to ensure only string inputs are processed. Organizations should also consider implementing runtime monitoring to detect anomalous memory allocation patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management practices and input validation, aligning with ATT&CK technique T1068 which covers local privilege escalation through memory corruption vulnerabilities. System hardening measures including stack canaries, address space layout randomization, and heap metadata protection can provide additional defense-in-depth layers against potential exploitation attempts.