{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/vendors/nyariv/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["@nyariv/sandboxjs (\u003c= 0.9.5)"],"_cs_severities":["critical"],"_cs_tags":["sandbox-escape","rce","javascript"],"_cs_type":"advisory","_cs_vendors":["nyariv"],"content_html":"\u003cp\u003eSandboxJS is a JavaScript sandbox environment that allows the execution of untrusted code in a controlled manner. A critical vulnerability, CVE-2026-43898, exists in versions 0.9.5 and earlier. This vulnerability allows a malicious actor to escape the sandbox and execute arbitrary JavaScript code on the host system. The vulnerability stems from the exposure of the \u003ccode\u003eFunction.caller\u003c/code\u003e property within the sandbox. By exploiting this property, sandboxed code can gain access to the internal \u003ccode\u003eLispType.Call\u003c/code\u003e runtime callback, enabling manipulation of the callback\u0026rsquo;s context and arguments to execute arbitrary commands. This vulnerability poses a significant risk, potentially leading to remote code execution (RCE) on systems utilizing the vulnerable SandboxJS package.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eThe attacker injects malicious JavaScript code into the SandboxJS environment.\u003c/li\u003e\n\u003cli\u003eThe injected code uses \u003ccode\u003eFunction.caller\u003c/code\u003e to obtain a reference to the internal \u003ccode\u003eLispType.Call\u003c/code\u003e runtime callback.\u003c/li\u003e\n\u003cli\u003eThe attacker crafts a fake \u003ccode\u003econtext\u003c/code\u003e and \u003ccode\u003eobj\u003c/code\u003e to pass as arguments to the leaked callback.\u003c/li\u003e\n\u003cli\u003eThe crafted context includes a \u003ccode\u003ecapture\u003c/code\u003e function that intercepts the internal function call within SandboxJS.\u003c/li\u003e\n\u003cli\u003eThe attacker uses the captured function to leak static properties of the \u003ccode\u003eObject\u003c/code\u003e constructor.\u003c/li\u003e\n\u003cli\u003eThe attacker obtains a reference to the host \u003ccode\u003eFunction\u003c/code\u003e constructor by calling internal primitive functions.\u003c/li\u003e\n\u003cli\u003eThe attacker crafts a string containing JavaScript code to execute on the host system.\u003c/li\u003e\n\u003cli\u003eThe attacker invokes the host \u003ccode\u003eFunction\u003c/code\u003e constructor with the malicious JavaScript code, resulting in remote code execution on the host.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of this vulnerability (CVE-2026-43898) allows an attacker to bypass the SandboxJS sandbox and execute arbitrary JavaScript code on the host system. This can lead to complete system compromise, including data theft, malware installation, and denial-of-service. Given the nature of sandboxes being used to execute untrusted code, the impact is typically critical. The vulnerability affects all users of \u003ccode\u003e@nyariv/sandboxjs\u003c/code\u003e versions 0.9.5 and earlier.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUpgrade the \u003ccode\u003e@nyariv/sandboxjs\u003c/code\u003e package to a version greater than 0.9.5 to patch CVE-2026-43898.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule \u0026ldquo;Detect SandboxJS Function Caller Abuse\u0026rdquo; to detect attempts to exploit the \u003ccode\u003eFunction.caller\u003c/code\u003e vulnerability.\u003c/li\u003e\n\u003cli\u003eMonitor JavaScript execution within SandboxJS environments for unexpected calls to \u003ccode\u003eFunction.caller\u003c/code\u003e.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2026-05-11T19:42:07Z","date_published":"2026-05-11T19:42:07Z","id":"https://feed.craftedsignal.io/briefs/2026-05-sandboxjs-escape/","summary":"SandboxJS is vulnerable to a sandbox escape (CVE-2026-43898); by exploiting the `Function.caller` property, sandboxed code can access the internal `LispType.Call` runtime callback, which allows an attacker to manipulate the context and arguments of the callback, leading to the execution of arbitrary host JavaScript and a complete sandbox escape.","title":"SandboxJS Function.caller Sandbox Escape Vulnerability (CVE-2026-43898)","url":"https://feed.craftedsignal.io/briefs/2026-05-sandboxjs-escape/"}],"language":"en","title":"CraftedSignal Threat Feed — Nyariv","version":"https://jsonfeed.org/version/1.1"}