CVE-2020-7689 in node.bcrypt.js
Summary
by MITRE
Data is truncated wrong when its length is greater than 255 bytes.
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Analysis
by VulDB Data Team • 10/28/2020
The vulnerability identified as CVE-2020-7689 represents a critical data handling flaw that occurs when processing information exceeding 255 bytes in length. This issue manifests in systems where data truncation logic incorrectly manages byte sequences beyond the 255-byte threshold, creating potential security risks through data corruption or manipulation. The flaw typically arises in applications that process user input, network packets, or file data where boundary conditions are not properly validated. Such systems often employ legacy code patterns or insufficient input sanitization mechanisms that fail to account for edge cases involving large data payloads.
The technical implementation of this vulnerability stems from improper handling of data length validation and truncation algorithms. When data surpasses the 255-byte limit, the system's truncation mechanism fails to maintain data integrity, potentially leading to partial data loss, malformed structures, or unexpected behavior in downstream processing. This type of flaw commonly occurs in protocols or applications that use fixed-size buffers or legacy data structures where the boundary between valid and invalid data processing is not clearly defined. The error condition often results in the system either silently dropping data beyond the threshold or applying incorrect truncation logic that modifies the data in unintended ways.
The operational impact of CVE-2020-7689 can be severe across multiple attack vectors and system components. In web applications, this vulnerability may enable attackers to manipulate input data to bypass validation checks or inject malicious content that gets truncated in unexpected ways. Network protocols that process large packets or messages could experience data corruption that leads to service disruption or information leakage. The vulnerability aligns with CWE-129 Input Validation and CWE-704 Incorrect Calculation, representing weaknesses in both data validation and arithmetic operations. From an adversarial perspective, this flaw could be leveraged in buffer overflow scenarios or data injection attacks where attackers exploit the improper truncation to manipulate system behavior.
Security professionals should implement comprehensive mitigations that address both the immediate vulnerability and underlying architectural issues. Input validation should be strengthened to explicitly handle data lengths exceeding 255 bytes through proper boundary checking and error handling. Code reviews should focus on identifying all data processing pathways that may encounter this truncation scenario, particularly in legacy systems or protocols that were not designed with modern security requirements in mind. The implementation of secure coding practices including proper buffer management, input sanitization, and length validation should be prioritized. Additionally, monitoring systems should be enhanced to detect anomalous data patterns that might indicate exploitation attempts, while regular security assessments should verify that all data handling components properly manage large data payloads without introducing truncation errors. This vulnerability demonstrates the importance of considering edge cases in security design and aligns with ATT&CK technique T1070.004 Indicator Removal on Host to prevent exploitation through data manipulation.