CVE-2026-117982 in Firefox
Summary
by MITRE • 10/27/2026
Invalid pointer in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability resides within the Just-In-Time compilation subsystem of the Mozilla SpiderMonkey JavaScript engine, specifically involving an invalid memory pointer dereference during the execution of optimized code paths. This type of flaw typically arises when the JIT compiler generates machine code that incorrectly assumes a certain data structure or object state remains valid and accessible in memory after it has been deallocated, modified, or moved by the garbage collector. In complex JavaScript applications where dynamic typing and frequent object creation occur, the optimizer may cache references to objects for performance gains. If these cached pointers are not properly invalidated when the underlying heap structures change, subsequent execution of JIT-compiled functions can attempt to read from or write to an invalid memory address. This represents a classic use-after-free scenario or a dangling pointer dereference, which falls under CWE-416 (Use After Free) and CWE-824 (Access of Uninitialized Pointer), depending on the specific state of the freed memory at the time of access.
The operational impact of this vulnerability is severe due to its potential for remote code execution in a sandboxed environment. Although Firefox employs multiple layers of security mitigations such as ASLR, DEP, and Content Sandbox restrictions, an invalid pointer dereference can often be exploited to achieve arbitrary read or write primitives. By carefully crafting malicious JavaScript that triggers the JIT compiler to generate specific assembly sequences, an attacker might manipulate memory layout to overwrite function pointers or virtual table entries within the browser process. This could allow for control flow hijacking, leading to full compromise of the user's system if sandbox escape techniques are combined with this initial foothold. The severity is further amplified by the fact that JIT vulnerabilities often bypass traditional stack-based protections because they operate in executable memory regions and involve complex heap management logic that is difficult to statically analyze without specialized fuzzing tools.
Mitigation strategies primarily rely on timely software updates, as indicated by the resolution in Firefox 159 and Firefox ESR 153.6. Users must ensure their browsers are updated to these versions or later to receive patches for this specific memory safety issue. For enterprise environments utilizing Extended Support Release channels, administrators should verify that automatic update policies are configured correctly to propagate security fixes promptly across all endpoints. Additionally, developers integrating JavaScript engines into custom applications should adhere strictly to Mozilla's guidelines on embedding SpiderMonkey and ensure they link against the latest stable releases of the engine library. From a defensive posture perspective, organizations can employ browser hardening techniques such as disabling unnecessary plugins or scripts that might trigger complex JIT optimizations in untrusted contexts. While no single mitigation eliminates all risks associated with memory corruption vulnerabilities, maintaining up-to-date software versions remains the most effective defense against exploitation of known flaws like this one. The ATT&CK framework categorizes such exploits under T1203 (Exploitation for Client Execution), highlighting the need for robust endpoint detection and response capabilities to identify anomalous behavior resulting from successful browser-based attacks.