CVE-2026-81525 in PHP Library
Summary
by MITRE • 08/27/2026
The MongoDB client library for PHP does not sufficiently sanitize special elements in application-supplied namespace identifiers before using them to construct the target namespace for database operations. An application that incorporates untrusted text into these identifiers may have operations silently directed at a different storage location than the one the application intended.
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability described involves a critical input validation failure within the MongoDB client library for PHP, specifically concerning the handling of namespace identifiers used in database operations. In NoSQL databases like MongoDB, namespaces typically refer to the combination of database name and collection name that uniquely identifies where data is stored. The core technical flaw lies in the insufficient sanitization of special characters or elements embedded within these application-supplied identifiers. When developers incorporate dynamic values into queries without rigorous validation, the library fails to properly escape or neutralize maliciously crafted inputs before constructing the final target namespace. This lack of proper encoding allows an attacker to manipulate the structural integrity of the query by injecting unintended delimiters or operators that alter the path resolution logic within the driver.
From a technical perspective, this flaw enables what is known as NoSQL injection via namespace manipulation. Unlike traditional SQL injection which targets query clauses like WHERE conditions, this vulnerability targets the metadata layer itself—the location where data resides. By exploiting insufficient sanitization of special elements such as dots or dollar signs in collection names, an attacker can redirect database operations to unintended collections. For instance, if a user-controlled input is used directly in a command that specifies a target collection, injecting specific characters might allow the operator to traverse into other databases or overwrite critical system collections. This results in silent redirection of data writes and reads, meaning the application continues to execute without throwing errors, but operates on completely different storage locations than intended by the developer logic.
The operational impact of this vulnerability is severe due to its potential for unauthorized access, data integrity compromise, and denial of service. Since operations are silently directed to a different storage location, an attacker could potentially read sensitive information from administrative or system collections that were not meant to be accessible through normal application flows. Conversely, the attacker might write malicious payloads into critical configuration stores or overwrite legitimate user data in unrelated collections, leading to widespread data corruption and loss of trust in the application's integrity. Furthermore, because the redirection is silent, security monitoring tools may fail to detect the anomaly immediately, allowing prolonged unauthorized access or persistent backdoors within the database structure before detection occurs.
This vulnerability aligns with CWE-94 Improper Control of Generation of Code (Code Injection) and more specifically CWE-1023 Improvement of Error Handling for Sensitive Information Exposure if it leads to data leakage, but primarily falls under CWE-78 Improper Neutralization of Special Elements used in an OS Command or similar injection vectors adapted for NoSQL contexts. In the context of the MITRE ATT&CK framework, this behavior maps to T1059 Command and Scripting Interpreter via API abuse or potentially T1190 Exploit Public-Facing Application if exploited remotely over HTTP. The lack of input validation on structural components like namespaces represents a fundamental failure in secure coding practices for dynamic query construction.
To mitigate this vulnerability, developers must implement strict allow-list validation for all namespace identifiers derived from user input rather than relying solely on blacklist approaches or generic escaping mechanisms that may not cover edge cases specific to MongoDB's parsing logic. It is essential to validate that database and collection names conform strictly to expected alphanumeric patterns and length constraints before passing them to the driver methods. Additionally, utilizing parameterized queries where supported by the library can help separate data from structural commands, although namespace parameters often require explicit validation since they are not always treated as simple values in all MongoDB shell operations. Regular security audits focusing on dynamic query construction and static analysis tools configured to detect NoSQL injection patterns should be integrated into the development lifecycle to prevent similar flaws.