CVE-2026-0821 identifies a heap-based buffer overflow vulnerability in the quickjs-ng quickjs JavaScript engine, specifically within the js_typed_array_constructor function located in quickjs.c. This vulnerability affects all versions up to and including 0.11.0. The flaw arises from improper handling of typed array construction, where crafted input can cause the function to write beyond the allocated heap buffer boundaries. This memory corruption can lead to undefined behavior such as application crashes or arbitrary code execution. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing its risk profile. The attack vector is network-based, allowing attackers to send malicious payloads to vulnerable quickjs instances embedded in applications or devices. The vulnerability was publicly disclosed shortly after being reserved, and a patch identified by commit c5d80831e51e48a83eab16ea867be87f091783c5 is available to remediate the issue. Despite no known active exploitation in the wild, the public disclosure and ease of exploitation make timely patching critical. The CVSS 4.0 score of 6.9 reflects medium severity, with low complexity and no privileges or user interaction required, but limited impact on confidentiality, integrity, and availability. Quickjs is often used in embedded systems, IoT devices, and lightweight JavaScript environments, which may be deployed in various European industries.

The heap-based buffer overflow in quickjs-ng quickjs can lead to arbitrary code execution or denial of service conditions, potentially compromising the confidentiality, integrity, and availability of affected systems. For European organizations, this poses a risk particularly in sectors relying on embedded systems, IoT devices, or applications that embed quickjs for scripting capabilities. Exploitation could allow attackers to execute malicious code remotely, leading to system takeover, data breaches, or disruption of critical services. The medium severity score indicates a moderate risk, but the lack of authentication and user interaction requirements increases the likelihood of exploitation. Industries such as manufacturing, telecommunications, and critical infrastructure in Europe that integrate quickjs in their technology stacks could face operational disruptions or security breaches if unpatched. Additionally, supply chain risks exist if third-party software or hardware vendors incorporate vulnerable quickjs versions. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially given the public availability of the vulnerability details and patch.

European organizations should immediately identify all instances of quickjs-ng quickjs in their environments, including embedded systems, IoT devices, and software applications. They must apply the official patch referenced by commit c5d80831e51e48a83eab16ea867be87f091783c5 to all affected versions up to 0.11.0. For systems where patching is not immediately feasible, implement network-level protections such as firewall rules to restrict access to services using quickjs, and deploy intrusion detection/prevention systems to monitor for suspicious payloads targeting the js_typed_array_constructor function. Conduct thorough code audits and penetration testing on applications embedding quickjs to detect potential exploitation attempts. Vendors and integrators should update their products to incorporate the patched quickjs version and communicate the urgency to customers. Additionally, implement runtime protections such as heap memory integrity checks and sandboxing to limit the impact of potential exploitation. Maintain up-to-date asset inventories to track vulnerable components and ensure rapid response to emerging threats related to this vulnerability.