CVE-2026-92022 in Firefox
Summary
by MITRE • 09/15/2026
Use-after-free in the DOM: HTML Parser 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 vulnerability resides within the Document Object Model HTML Parser component of Mozilla Firefox browsers, representing a critical class of memory corruption issues known as use-after-free errors. This specific flaw occurs when the browser's rendering engine continues to reference a block of memory that has already been deallocated by the system. In the context of web page parsing, this typically happens during the complex process of interpreting HTML structures where dynamic updates or script execution trigger rapid allocation and release cycles for internal parser objects. If an attacker can craft a malicious webpage that manipulates these timing conditions or object lifecycles, they may cause the browser to access freed memory locations, leading to undefined behavior within the application's runtime environment.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow attackers to control what data is read from or written to the invalid memory pointer. By carefully constructing exploit code that allocates new objects in the same memory space previously occupied by the freed parser object, an attacker can achieve arbitrary code execution with the privileges of the victim user. This mechanism bypasses many modern browser security mitigations such as heap randomization and data execution prevention because it exploits logical errors in memory management rather than simple buffer overflows. The HTML Parser is a high-value target for exploitation due to its central role in rendering web content, meaning that simply visiting a compromised website could trigger the vulnerability without any additional user interaction beyond loading the page.
The operational impact of this vulnerability is severe, potentially leading to complete compromise of the end-user's system. Successful exploitation allows remote attackers to execute arbitrary code on the victim's machine, which can result in data theft, installation of malware, or use of the compromised browser as a pivot point for further network attacks. Given that Firefox is widely used across enterprise and personal environments, this vulnerability poses a significant risk to organizational security postures if left unpatched. The lack of user interaction required makes it suitable for drive-by download attacks where victims are lured to malicious sites through phishing or compromised advertising networks.
To mitigate the risks associated with this flaw, organizations must ensure that all instances of Firefox and its Extended Support Release (ESR) variants are updated immediately. Specifically, users should upgrade to Firefox version 156, Firefox ESR 115.41, Firefox ESR 140.16, or Firefox ESR 153.3, as these versions contain the necessary patches that correct the memory management logic within the HTML Parser. For enterprise environments, automated patching solutions should be configured to prioritize this update due to its high severity rating. Additionally, implementing browser isolation technologies and restricting script execution on untrusted domains can provide an additional layer of defense against exploitation attempts while updates are being deployed across the infrastructure.
This vulnerability aligns with Common Weakness Enumeration (CWE) identifier CWE-416, which describes use-after-free conditions where a pointer is used after it has been freed, leading to unpredictable behavior and potential security breaches. In terms of offensive cybersecurity frameworks, this flaw facilitates techniques categorized under MITRE ATT&CK Tactic TA0002 Execution, specifically enabling remote code execution through browser vulnerabilities. Understanding these mappings helps security teams prioritize remediation efforts based on standardized risk assessments and align their defense strategies with industry best practices for mitigating memory corruption attacks in web browsers.