CVE-2022-38475 in Firefox
Summary
by MITRE • 12/22/2022
An attacker could have written a value to the first element in a zero-length JavaScript array. Although the array was zero-length, the value was not written to an invalid memory address. This vulnerability affects Firefox < 104.
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Analysis
by VulDB Data Team • 06/22/2026
This vulnerability represents a memory safety issue in the JavaScript engine of Mozilla Firefox browsers, specifically affecting versions prior to 104. The flaw occurs within the engine's handling of zero-length arrays, where an attacker could potentially manipulate memory operations that should not be possible given the array's size constraints. The vulnerability falls under the category of buffer over-read conditions and memory corruption issues that can lead to arbitrary code execution. According to CWE-129, this represents an insufficient input validation scenario where the system fails to properly validate array boundaries and memory access permissions. The issue stems from the JavaScript engine's failure to properly enforce array size limitations when processing zero-length arrays, creating a potential attack surface that could be exploited by malicious actors.
The technical implementation of this vulnerability involves the JavaScript engine's memory management system where it processes array operations without adequate boundary checking for zero-length arrays. When an attacker attempts to write a value to the first element of such an array, the system should reject this operation due to the array's zero length. However, the flaw allows this write operation to proceed, potentially leading to memory corruption that could be leveraged for privilege escalation or code execution. The vulnerability demonstrates a classic case of improper input validation where the system fails to properly validate array access permissions against array size constraints. This behavior creates a potential path for attackers to manipulate memory locations that should remain inaccessible, effectively bypassing normal memory protection mechanisms that are typically enforced for zero-length data structures.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a potential pathway for remote code execution in the context of web browser exploitation. Attackers could craft malicious JavaScript code that takes advantage of this flaw to execute arbitrary commands within the browser's security context, potentially leading to complete system compromise. The vulnerability affects not only the targeted browser but also represents a broader concern for web application security, as it demonstrates how seemingly minor implementation flaws in core systems can create significant security risks. This issue aligns with ATT&CK technique T1059.007 for JavaScript and T1203 for Exploitation for Client Execution, as it provides an attack vector that could be used to execute malicious code within the browser environment.
Mitigation strategies for this vulnerability primarily focus on immediate browser updates to version 104 or later, where the underlying memory management issues have been addressed through enhanced boundary checking and validation. Organizations should implement comprehensive patch management procedures to ensure all affected systems receive updates promptly. Additionally, browser hardening measures such as sandboxing, content security policies, and strict MIME type checking can provide additional defense layers against exploitation attempts. Security teams should monitor for indicators of compromise related to this vulnerability, particularly unusual JavaScript execution patterns or attempts to access zero-length array elements. The fix implemented by Mozilla addresses the core validation issue by ensuring that array operations properly respect size constraints and prevent memory access violations that could occur with zero-length arrays. System administrators should also consider implementing web application firewalls and intrusion detection systems that can identify and block malicious JavaScript payloads attempting to exploit this specific vulnerability pattern.