CVE-2026-100773 in Firefox
Summary
by MITRE • 09/29/2026
Use-after-free in the Storage: IndexedDB component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
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Analysis
by VulDB Data Team • 09/29/2026
The identified vulnerability represents a critical memory management error within the IndexedDB component of Mozilla Firefox, specifically classified as an out-of-bounds write resulting from use-after-free conditions. This type of flaw occurs when the application continues to reference a memory block after it has been freed or deallocated by the system. In the context of browser engines and database storage subsystems like IndexedDB, such errors are particularly dangerous because they can lead to arbitrary code execution with the privileges of the user running the browser. The root cause typically involves a race condition or improper lifecycle management where an object is destroyed while still being accessed by another part of the application logic, leading to the reuse of that memory address for new data structures without proper validation.
From a technical perspective, this vulnerability falls under CWE-416, which describes use-after-free errors. The exploitation potential is significant because attackers can craft malicious web content or scripts that trigger specific sequences within the IndexedDB API. By manipulating the timing and state of database operations, an attacker might cause the browser to write data into a freed memory region. If this overwritten memory happens to contain function pointers or object headers used by the JavaScript engine or the rendering process, it can allow for control flow hijacking. This mechanism is often leveraged in drive-by download attacks where visiting a compromised website could lead to remote code execution without any user interaction beyond loading the page.
The operational impact of this vulnerability extends beyond simple data corruption. Successful exploitation allows an attacker to execute arbitrary commands on the victim's machine, potentially leading to full system compromise. This includes stealing sensitive information stored in IndexedDB such as session tokens, personal identifiers, or financial data that applications persist locally for performance reasons. Furthermore, because browsers operate with varying levels of sandboxing depending on the operating system and configuration, a successful exploit might allow an attacker to escape the browser's security container and interact directly with the host operating system. This elevates the threat from a local information disclosure issue to a critical remote code execution vulnerability affecting user confidentiality, integrity, and availability.
In terms of industry frameworks, this incident aligns with MITRE ATT&CK techniques related to initial access via web-based delivery and subsequent privilege escalation or defense evasion through memory corruption. The specific behavior maps to tactics involving exploitation for credential theft or lateral movement if the compromised browser is used as a pivot point within an enterprise network. Security researchers often categorize such vulnerabilities under high-severity ratings due to their prevalence in complex software like browsers and their direct impact on user security posture.
Mitigation strategies primarily involve immediate patching through the provided updates, which include Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. These releases contain code changes that enforce stricter memory management protocols within the IndexedDB implementation, ensuring that objects are properly invalidated after deallocation or preventing access to freed memory regions entirely. Organizations should prioritize updating all endpoints running affected versions of Firefox to eliminate this attack vector. Additionally, implementing strict content security policies and disabling unnecessary JavaScript execution on untrusted sites can reduce the likelihood of triggering such vulnerabilities in legacy systems where immediate patching is not feasible. Regular monitoring for browser updates and enforcing automated update mechanisms are essential practices to maintain resilience against memory corruption exploits.