CVE-2026-25142 is a critical vulnerability classified under CWE-94 (Improper Control of Generation of Code) affecting the SandboxJS library, a JavaScript sandboxing tool designed to safely execute untrusted code. Prior to version 0.8.27, SandboxJS fails to properly restrict the __lookupGetter__ method, a JavaScript feature that allows access to property getters on an object's prototype chain. By exploiting this flaw, an attacker can retrieve prototype objects and subsequently execute arbitrary code outside the sandbox constraints, effectively escaping the sandbox environment. This leads to remote code execution (RCE) on the host system where SandboxJS is deployed. The vulnerability requires no authentication or user interaction and can be exploited remotely over the network, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H). The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component. The impact includes full compromise of confidentiality, integrity, and availability of affected systems. Although no public exploits have been reported yet, the critical nature and ease of exploitation make this a high-priority threat. The issue was publicly disclosed on February 2, 2026, and fixed in SandboxJS version 0.8.27. Organizations using earlier versions should urgently upgrade and review sandbox configurations to prevent exploitation.

For European organizations, the impact of CVE-2026-25142 is severe. Organizations that rely on SandboxJS for isolating and securely executing JavaScript code—such as web application providers, SaaS platforms, and development environments—face the risk of full system compromise. An attacker exploiting this vulnerability can execute arbitrary code remotely, leading to data breaches, service disruption, and potential lateral movement within networks. Critical infrastructure and industries with high regulatory requirements (finance, healthcare, government) are particularly vulnerable due to the potential exposure of sensitive data and operational disruption. The vulnerability’s ability to bypass sandbox protections undermines trust in security controls, increasing the risk of supply chain attacks if SandboxJS is embedded in third-party software. The absence of required authentication and user interaction lowers the barrier for attackers, increasing the likelihood of exploitation. The critical CVSS score reflects the potential for widespread damage across confidentiality, integrity, and availability domains.

European organizations should immediately upgrade SandboxJS to version 0.8.27 or later to remediate this vulnerability. If upgrading is not immediately feasible, organizations should implement strict input validation and restrict the use of __lookupGetter__ and similar prototype-access methods within sandboxed code. Employ runtime monitoring and anomaly detection to identify unusual sandbox escape attempts. Review and harden sandbox configurations to limit access to sensitive APIs and system resources. Conduct thorough code audits to identify any indirect usage of vulnerable SandboxJS versions in dependencies or third-party components. Implement network segmentation and least privilege principles to contain potential breaches. Additionally, maintain up-to-date incident response plans to quickly address any exploitation attempts. Regularly monitor threat intelligence feeds for emerging exploits related to this CVE.