CVE-2026-92027 in Firefox
Summary
by MITRE • 09/15/2026
Use-after-free in the DOM: Streams 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 represents a critical memory management error within the Document Object Model streams component of Mozilla Firefox browsers. Specifically classified as an use-after-free condition, this flaw occurs when the application attempts to access memory that has already been deallocated by the system. In the context of DOM Streams, which handle asynchronous data processing and transfer between different execution contexts such as web workers or service workers, proper lifecycle management is essential. When a stream object is closed or garbage collected, its underlying buffer resources are released back to the operating system. However, due to a logic error in the reference counting or state tracking mechanisms within this component, certain code paths may retain stale pointers to these freed memory regions. If subsequent operations attempt to read from or write to these invalid addresses, it triggers undefined behavior that can lead to application crashes or more severe security compromises.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow an attacker to manipulate the state of the program after critical resources have been relinquished. In modern browsers, memory corruption bugs like this one often serve as stepping stones for arbitrary code execution attacks. An adversary could potentially craft malicious web content that triggers the premature deallocation of a stream object while maintaining references to it through other active DOM nodes or event handlers. By carefully controlling the allocation and freeing patterns in heap memory, an attacker might be able to overwrite adjacent objects with controlled data structures. This technique can lead to type confusion scenarios where the browser interprets user-controlled input as executable code or internal pointers, thereby bypassing standard security mitigations such as stack canaries or address space layout randomization depending on the specific exploitation context and target architecture.
The operational impact of this vulnerability is significant for users relying on Firefox-based browsers for secure web interactions. While a simple crash results in a denial-of-service condition that disrupts user productivity, the potential for remote code execution poses a far greater threat to data integrity and system security. If successfully exploited, an attacker could gain the same privileges as the current user, allowing them to steal sensitive information such as cookies, session tokens, or saved passwords stored by the browser. Furthermore, this access can be leveraged to install malware, establish persistent backdoors, or pivot into internal network segments if the victim is part of a corporate environment with less stringent endpoint protection policies. The risk is exacerbated in environments where users frequently interact with untrusted third-party websites that may embed malicious scripts designed specifically to trigger these memory corruption conditions within the streams API implementation.
Industry standards classify this type of flaw under CWE-416, which denotes Use After Free vulnerabilities. This classification highlights the fundamental failure in managing dynamic memory allocation and deallocation cycles correctly. In terms of offensive security frameworks, such as MITRE ATT&CK, this vulnerability aligns with techniques related to Memory Corruption (T1209) and potentially Exploitation for Privilege Escalation if it leads to higher-level access. The specific component involved, DOM Streams, falls under the broader category of browser engine vulnerabilities that are frequently targeted in advanced persistent threat campaigns due to their complexity and prevalence across major web platforms. Understanding these mappings helps security teams prioritize patching efforts based on both the severity of the underlying memory error and its potential for exploitation in real-world attack scenarios involving social engineering or drive-by downloads.
To mitigate the risks associated with this vulnerability, immediate action is required to update all affected installations to patched versions. The issue has been resolved in Firefox version 156 as well as specific extended support release branches including ESR 115.41, ESR 140.16, and ESR 153.3. Organizations should enforce automated patch management policies to ensure that all endpoints running these browser versions are updated promptly upon the availability of security updates. Additionally, implementing application whitelisting or strict content security policies can help reduce the attack surface by preventing unauthorized scripts from executing within the browser environment. For developers building web applications, it is advisable to audit code for complex stream manipulations and ensure that references to DOM objects are properly nullified when no longer needed to prevent accidental retention of pointers in edge cases. Regular vulnerability scanning and penetration testing focused on memory safety issues can further help identify similar latent defects before they are exploited by malicious actors targeting the broader user base.