CVE-2026-100813 in Firefox
Summary
by MITRE • 09/29/2026
Invalid pointer in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 157.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/29/2026
The identified vulnerability resides within the Just-In-Time (JIT) compilation subsystem of the Mozilla SpiderMonkey JavaScript engine, specifically involving an invalid memory pointer dereference. In modern web browsers, the JIT compiler is responsible for translating high-level JavaScript code into optimized machine code to enhance execution performance. This process involves complex memory management operations where variables and objects are mapped to specific locations in the heap or stack. The flaw arises when the JIT compiler fails to properly validate a pointer before attempting to access it, leading to a situation where the engine attempts to read from or write to an invalid memory address. Such errors typically stem from race conditions during garbage collection cycles, incorrect assumptions about object lifetimes, or failures in bounds checking within optimized code paths that handle complex data structures like arrays or objects with dynamic properties.
From a technical perspective, this type of vulnerability is classified under CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer and more specifically as an invalid pointer dereference which can lead to memory corruption. When the JIT engine executes generated code that relies on an invalidated or nullified pointer, it disrupts the integrity of the browser's process memory space. Depending on the specific state of the heap at the time of exploitation, this could result in a crash causing a denial of service for the user session. However, more critically, invalid pointer dereferences can be leveraged to achieve arbitrary code execution if an attacker can control the data pointed to by the invalid reference or manipulate memory layout through techniques such as heap spraying or type confusion attacks. This aligns with MITRE ATT&CK technique T1203 Exploitation for Client Execution, where malicious web content is used to trigger native application vulnerabilities on the client side.
The operational impact of this vulnerability varies based on whether it can be reliably exploited in a real-world scenario. If limited to memory corruption without code execution capabilities, the primary consequence is browser instability and potential data loss due to unexpected tab or process crashes. However, given that JIT engines are deeply integrated into the core rendering pipeline, successful exploitation could allow an attacker to bypass modern security mitigations such as Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP). An adversary hosting a malicious webpage containing crafted JavaScript payloads could trigger this flaw during page load or interaction, potentially gaining control over the browser process. This level of access enables further attacks including credential theft via cookie manipulation, keylogging through DOM event injection, or pivoting to attack other applications running on the same system if sandboxing mechanisms are insufficiently configured.
Mozilla addressed this issue in Firefox version 157 by implementing stricter validation checks within the JIT compiler's code generation phase and enhancing runtime assertions to detect invalid pointer states earlier in the execution flow. To mitigate risks associated with similar vulnerabilities, users should ensure their browsers are updated to the latest stable release which includes these security patches. Additionally, organizations can reduce exposure by enforcing strict Content Security Policy (CSP) headers that restrict inline script execution and prevent loading of untrusted third-party scripts. For developers integrating web technologies into native applications using embedded browser components like GeckoView or CEF, it is crucial to pin the underlying engine version to a secure baseline and regularly audit dependencies for known vulnerabilities in JavaScript engines. Regular security audits focusing on memory safety patterns in custom JS bindings can also help identify potential weak points before they are exploited by threat actors leveraging automated vulnerability discovery tools.