CVE-2025-62491
A Use-After-Free (UAF) vulnerability exists in the QuickJS engine's standard library when iterating over the global list of unhandled rejected promises (ts->rejected_promise_list).
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The function js_std_promise_rejection_check attempts to iterate over the rejected_promise_list to report unhandled rejections using a standard list loop.
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The reason for a promise rejection is processed inside the loop, including calling js_std_dump_error1(ctx, rp->reason).
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If the promise rejection reason is an Error object that defines a custom property getter (e.g., via Object.defineProperty), this getter is executed during the error dumping process.
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The malicious custom getter can execute JavaScript code that calls catch() on the same rejected promise being processed.
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Calling catch() internally triggers js_std_promise_rejection_tracker, which then removes and frees the current promise entry (JSRejectedPromiseEntry) from the rejected_promise_list.
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Since the list iteration continues using the now-freed memory pointer (el), the subsequent loop access results in a Use-After-Free condition.
| Software | From | Fixed in |
|---|---|---|
| quickjs_project / quickjs | - | 2025-09-13 |
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A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.
Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
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