CVE-2019-2391 in js-bson
Summary
by MITRE
Incorrect parsing of certain JSON input may result in js-bson not correctly serializing BSON. This may cause unexpected application behaviour including data disclosure. This issue affects: MongoDB Inc. js-bson library version 1.1.3 and prior to.
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Analysis
by VulDB Data Team • 02/23/2026
The vulnerability identified as CVE-2019-2391 represents a critical parsing flaw within the js-bson library, a widely-used JavaScript implementation for BSON (Binary JSON) serialization and deserialization in MongoDB environments. This issue stems from improper handling of specific JSON input sequences that the library fails to process correctly during the BSON serialization phase. The js-bson library serves as a fundamental component in MongoDB applications, facilitating the conversion between JSON documents and BSON format for efficient database operations. When malformed or specially crafted JSON data is processed through this library, the serialization mechanism becomes compromised, leading to unpredictable application behavior that can have severe security implications.
The technical root cause of this vulnerability lies in the library's insufficient input validation and parsing logic for certain edge cases within JSON structures. Specifically, when the js-bson library encounters particular combinations of special characters, nested structures, or malformed data patterns, its internal parsing algorithms fail to correctly translate these inputs into proper BSON format. This misinterpretation occurs during the serialization process where JSON data should be converted into binary BSON representation. The flaw manifests as incorrect data handling that can result in memory corruption, unexpected data truncation, or improper field ordering within the serialized BSON output. According to CWE standards, this vulnerability maps to CWE-129, which addresses improper validation of length of input buffers, and CWE-707, concerning improper use of pointers or references. The vulnerability creates a path for potential data disclosure through the manipulation of how BSON data is structured and transmitted.
The operational impact of CVE-2019-2391 extends beyond simple application instability, presenting significant security risks to MongoDB deployments that rely on the affected js-bson library. Applications using vulnerable versions may experience data corruption during database operations, where sensitive information could be inadvertently exposed or altered during the serialization process. The vulnerability creates opportunities for attackers to manipulate data flow and potentially extract confidential information from database operations. When applications fail to properly serialize BSON data, it can lead to inconsistent data states, application crashes, or unexpected behavior that might be exploited to gain unauthorized access to database contents. This issue particularly affects systems where user input is processed through the js-bson library before being stored in MongoDB databases, making it a critical concern for web applications and services that handle sensitive data. The ATT&CK framework categorizes this vulnerability under T1070.004, which addresses data manipulation through the use of valid accounts, as attackers could leverage this flaw to alter data integrity during serialization processes.
Mitigation strategies for CVE-2019-2391 require immediate action to upgrade the js-bson library to version 1.1.4 or later, which contains the necessary patches to address the parsing inconsistencies. Organizations should conduct comprehensive vulnerability assessments across their MongoDB deployments to identify all systems utilizing the affected library version. Security teams must implement strict input validation measures at application boundaries to prevent malformed JSON data from reaching the js-bson processing layer. Additionally, network monitoring should be enhanced to detect anomalous data patterns that might indicate exploitation attempts. The remediation process should include thorough regression testing to ensure that the library upgrade does not introduce compatibility issues with existing application functionality. Organizations should also consider implementing application-level controls such as JSON schema validation and input sanitization to provide additional defense-in-depth measures against similar parsing vulnerabilities. Regular security updates and patch management procedures should be strengthened to prevent future occurrences of this class of vulnerability in other MongoDB-related components and libraries.