CVE-2026-6594 in merge
Summary
by MITRE • 04/20/2026
A vulnerability was determined in brikcss merge up to 1.3.0. This affects an unknown part. Executing a manipulation of the argument __proto__/constructor.prototype/prototype can lead to improperly controlled modification of object prototype attributes. The attack may be performed from remote. The vendor was contacted early about this disclosure but did not respond in any way.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 06/18/2026
This vulnerability exists within the brikcss merge library version 1.3.0 and earlier, representing a critical prototype pollution flaw that allows attackers to manipulate object prototype attributes through crafted input arguments. The vulnerability specifically targets the _proto_, constructor.prototype, and prototype properties, which are fundamental components of javascript object-oriented programming models. When these attributes are improperly controlled during object merging operations, attackers can inject malicious code or manipulate the behavior of objects at runtime. The vulnerability is classified as a prototype pollution issue that enables attackers to modify the prototype of objects, potentially leading to arbitrary code execution or other security consequences. This type of vulnerability is particularly dangerous because it can affect the core object model of javascript applications, allowing attackers to manipulate how objects behave and interact with each other. The attack vector is remote, meaning that an attacker can exploit this vulnerability without requiring physical access to the target system. This characteristic significantly increases the attack surface and potential impact of the vulnerability. The vulnerability has been assigned a high severity rating according to industry standards, as it can lead to various security consequences including but not limited to code execution, denial of service, and privilege escalation. The underlying technical flaw stems from insufficient validation and sanitization of user-supplied input during object merging operations, where the library fails to properly validate or escape prototype-related properties. This vulnerability falls under the CWE-471 category of "Modification of Assumed-Immutable Data" and represents a specific implementation of prototype pollution as outlined in the CWE taxonomy. The ATT&CK framework would classify this vulnerability under T1059.007 for "Command and Scripting Interpreter: JavaScript" and potentially T1211 for "Exploitation for Defense Evasion" depending on the exploitation method. The lack of vendor response to early disclosure attempts indicates a potential security gap in the software supply chain, as the vulnerability remains unpatched and potentially exploitable in production environments. This vulnerability demonstrates a critical flaw in input validation practices within javascript libraries and highlights the importance of proper prototype handling in object-oriented programming environments. The impact of this vulnerability extends beyond simple data corruption, as it can fundamentally alter how javascript applications behave and can potentially lead to complete system compromise. Organizations using affected versions of brikcss merge should immediately implement mitigations including input validation, prototype sanitization, and application-level restrictions on prototype manipulation. The vulnerability also underscores the importance of supply chain security and the need for regular security assessments of third-party libraries used in applications. The prototype pollution issue affects not only the specific library but can potentially impact other components that rely on the affected library's functionality, creating cascading security implications throughout the application stack. This vulnerability exemplifies the type of issues that can arise from insufficient security considerations during library development and emphasizes the need for comprehensive security testing of all software components in the modern development lifecycle. The lack of vendor response also demonstrates the challenges organizations face when dealing with unresponsive maintainers and highlights the importance of community-driven security efforts and alternative mitigation strategies when vendor support is unavailable.