CVE-2026-92023 in Firefox
Summary
by MITRE • 09/15/2026
Use-after-free in the XML component. This vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security flaw represents a critical use-after-free condition located within the XML processing component of Mozilla Firefox browsers. This type of vulnerability arises when memory that has already been deallocated is subsequently accessed by the application logic. In the context of web browser engines, such errors typically occur during the parsing and rendering of complex or malformed XML documents where lifecycle management of internal data structures fails to synchronize correctly with user input or network responses. The specific nature of this flaw suggests that an object was freed while references to it remained active in memory, creating a window for exploitation before those dangling pointers are nullified or overwritten by subsequent operations.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow attackers to manipulate the heap layout and potentially achieve arbitrary code execution with the privileges of the victim process. When an attacker can control what data is written into the freed memory region through crafted XML content, they may be able to overwrite function pointers or object vtables. This manipulation enables the injection and subsequent execution of malicious shellcode during the next dereference operation. The vulnerability affects multiple versions of Firefox including version 156 as well as several Extended Support Release (ESR) branches such as 115.41, 140.16, and 153.3, indicating that the underlying parsing logic shared across these builds contained a systemic defect in memory management protocols for XML nodes or related metadata structures.
The operational impact of this vulnerability is severe, posing significant risks to end-users who encounter maliciously crafted web pages containing embedded XML payloads. Successful exploitation could lead to remote code execution, allowing an attacker to take control of the affected system, install malware, exfiltrate sensitive data such as credentials and browsing history, or establish persistent access within the network environment. Since browsers operate with varying levels of sandboxing depending on configuration and version, a successful exploit might also facilitate sandbox escape techniques if additional vulnerabilities are chained together. The presence in ESR versions is particularly concerning because these releases often remain deployed across enterprise environments for extended periods without immediate patching cycles comparable to standard release channels.
Industry standards classify this flaw under CWE-416 which denotes use-after-free errors, a category of memory corruption bugs that consistently rank among the most prevalent and dangerous software defects in modern applications. In terms of tactical mapping within the MITRE ATT&CK framework, exploitation of such vulnerabilities aligns with techniques related to initial access via drive-by compromise or execution through browser-based attacks where malicious content is delivered over HTTPS to evade network security controls. The attack vector typically involves convincing a user to visit a specially crafted website that triggers the vulnerable XML parser during page load or interaction events.
Mitigation strategies primarily involve immediate software updates as provided by Mozilla in the specified versions. Organizations relying on Firefox ESR branches must ensure their update policies are configured to automatically deploy these patches to all endpoints without delay. For users unable to upgrade immediately, network-level defenses such as web proxies with deep packet inspection capabilities can be employed to detect and block requests containing suspicious XML structures known to trigger this specific memory corruption pattern. Additionally enabling strict content security policies and disabling unnecessary browser features like automatic plugin execution or script access from untrusted origins can reduce the attack surface available to potential exploiters until full remediation is achieved across all systems.