CVE-2026-16369 in Firefox
Summary
by MITRE • 07/21/2026
Integer overflow in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13.
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Analysis
by VulDB Data Team • 07/21/2026
This integer overflow vulnerability resides within the JavaScript WebAssembly component of Mozilla Firefox browsers, representing a critical security flaw that could potentially allow remote code execution or system compromise. The vulnerability stems from improper handling of integer values during WebAssembly module processing, specifically when dealing with large numerical operations that exceed the maximum representable value for the target integer type. Such flaws typically arise from insufficient bounds checking and overflow validation mechanisms in the underlying WebAssembly interpreter implementation. The issue affects both regular Firefox releases and Extended Support Release versions, indicating a widespread impact across Mozilla's browser distribution channels.
The technical nature of this vulnerability places it squarely within the realm of CWE-190, which specifically addresses integer overflow conditions where an integer is incremented beyond its maximum value, or decremented below its minimum value. When processing WebAssembly modules that contain maliciously crafted integer values, the JavaScript engine fails to properly validate these inputs against the maximum limits of their respective data types. This allows attackers to manipulate integer arithmetic operations in ways that can bypass intended security boundaries and potentially corrupt memory structures. The exploitation typically involves crafting WebAssembly code with intentionally oversized integer parameters that cause the interpreter to behave unpredictably when performing calculations or memory allocations.
The operational impact of this vulnerability extends beyond simple browser instability, as it provides potential attack vectors for sophisticated exploitation techniques. Attackers could leverage this flaw through malicious websites or WebAssembly modules delivered via phishing campaigns, leading to arbitrary code execution on vulnerable systems. The attack surface is particularly concerning given that WebAssembly is designed to enable high-performance applications within web browsers, making it a common target for advanced persistent threats. According to ATT&CK framework category T1203, this vulnerability could be exploited through malicious web content delivery, potentially enabling threat actors to establish footholds on target systems and escalate privileges.
Mitigation strategies should prioritize immediate patch deployment across all affected Firefox installations, including both regular releases and ESR versions. Organizations should implement browser hardening measures such as disabling WebAssembly when not required for specific applications, employing content security policies that restrict execution of potentially malicious code, and monitoring network traffic for suspicious WebAssembly module deliveries. Additionally, implementing regular vulnerability assessments and penetration testing focused on browser-based attack surfaces can help identify potential exploitation paths before they are actively leveraged by threat actors. Security teams should also consider deploying web application firewalls that can detect and block malicious WebAssembly content, while maintaining updated threat intelligence feeds to monitor for related exploitation attempts targeting this specific vulnerability class.