CVE-2026-117935 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the DOM: Bindings (WebIDL) component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability represents a critical memory management error within the Document Object Model bindings layer of Mozilla Firefox, specifically affecting the WebIDL component used to bridge JavaScript interfaces with C++ backend implementations. This class of flaw is categorized under CWE-416 as an Use After Free condition, where a program continues to use a pointer after it has been freed from memory. In the context of browser engines like Gecko, this typically occurs when the lifecycle management of DOM objects and their corresponding JavaScript wrappers becomes desynchronized. When a web page manipulates complex DOM structures or triggers specific event handlers that cause rapid object creation and destruction, the underlying C++ code may release the memory associated with an internal data structure while a reference to that same memory location is still held by the JavaScript engine or another active component within the browser process.
From a technical perspective, this flaw arises in the bindings layer where WebIDL interfaces define how web content interacts with native code. If the garbage collector or manual memory management routines fail to properly invalidate dangling pointers before they are accessed again, the application attempts to read from or write to an address that has already been returned to the system allocator. This state is particularly dangerous because the freed memory may have been reallocated for a different purpose by subsequent operations within the same process. Consequently, any data written through the stale pointer will corrupt unrelated objects in memory, while reading from it yields unpredictable values based on whatever new object currently occupies that space. The vulnerability was addressed and patched in Firefox version 159 as well as specific maintenance releases of the Extended Support Release channels, namely ESR 115.44 and ESR 153.6, ensuring that developers relying on stable versions have access to these critical security fixes.
The operational impact of this vulnerability is severe due to its potential for remote code execution. Attackers can craft malicious web pages containing specially designed JavaScript sequences that trigger the specific conditions required to induce the use-after-free state within the DOM bindings. By carefully controlling memory allocation patterns, an attacker can manipulate the heap layout so that when the stale pointer is dereferenced, it accesses a controlled object structure rather than random data. This allows for arbitrary read and write primitives, which are foundational steps in building exploit chains to bypass modern browser security mitigations such as ASLR and DEP. Successful exploitation could lead to full compromise of the user's system, allowing unauthorized access to sensitive files, installation of malware, or use of the machine as part of a botnet.
Mitigation strategies primarily involve ensuring that all systems running Firefox are updated to the latest stable versions containing these patches. For organizations managing large fleets of endpoints, automated patch management tools should be configured to prioritize updates for browsers with known memory corruption vulnerabilities. Additionally, users can reduce their exposure by disabling JavaScript on untrusted sites or using browser extensions that restrict script execution in high-risk environments. From a development standpoint, adhering strictly to WebIDL specifications and ensuring rigorous testing of DOM manipulation scenarios helps prevent similar issues in future releases. Security teams should also monitor for indicators of compromise related to heap spraying techniques often associated with this type of exploitation vector within the ATT&CK framework under T1203 Exploitation for Client Execution.