CVE-2015-0828 in Firefox
Summary
by MITRE
Double free vulnerability in the nsXMLHttpRequest::GetResponse function in Mozilla Firefox before 36.0, when a nonstandard memory allocator is used, allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via crafted JavaScript code that makes an XMLHttpRequest call with zero bytes of data.
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Analysis
by VulDB Data Team • 03/10/2022
The CVE-2015-0828 vulnerability represents a critical double free error in Mozilla Firefox's nsXMLHttpRequest::GetResponse function that emerged in versions prior to 36.0. This flaw manifests specifically when the browser employs a nonstandard memory allocator, creating a dangerous condition that can be exploited by remote attackers through carefully crafted JavaScript code. The vulnerability resides in the memory management subsystem of Firefox's XMLHttpRequest implementation, which handles asynchronous communication between web applications and servers. When an XMLHttpRequest call is made with zero bytes of data, the function fails to properly manage memory allocation and deallocation sequences, leading to a scenario where the same memory block is freed twice.
The technical execution of this vulnerability involves a specific memory corruption pattern that occurs during the processing of XMLHttpRequest responses. The double free condition arises from improper handling of memory deallocation within the nsXMLHttpRequest::GetResponse function, where the same memory address is passed to the free() function twice. This memory corruption can be leveraged to overwrite critical memory structures or execute arbitrary code within the context of the browser process. The vulnerability is particularly dangerous because it can be triggered through web-based JavaScript execution without requiring any special privileges or user interaction beyond visiting a malicious website. The flaw falls under CWE-415, which specifically addresses double free conditions in memory management, and aligns with ATT&CK technique T1059.007 for JavaScript-based exploitation.
The operational impact of this vulnerability extends beyond simple denial of service to encompass full remote code execution capabilities, making it a severe threat to web application security. Attackers can craft malicious web pages that, when loaded in Firefox, trigger the double free condition and potentially gain control over the victim's browser session. This could lead to session hijacking, data theft, or complete system compromise depending on the execution environment. The vulnerability affects users running Firefox versions earlier than 36.0, which represents a significant portion of the user base during the affected period. The memory corruption resulting from the double free can cause unpredictable behavior including crashes, memory corruption, or more sinisterly, code execution that bypasses standard security mitigations.
Organizations and users should immediately update to Firefox version 36.0 or later to remediate this vulnerability, as the fix addresses the underlying memory management flaw in the XMLHttpRequest implementation. The patch implemented by Mozilla corrects the improper memory deallocation sequence within the nsXMLHttpRequest::GetResponse function, preventing the double free condition from occurring. Security teams should also consider implementing additional network-level protections such as web application firewalls and content security policies to mitigate potential exploitation attempts. Regular security assessments of web applications should include checks for vulnerable Firefox versions, and administrators should monitor for any signs of exploitation attempts targeting this specific vulnerability. The remediation process should also involve user education about the importance of keeping browser software updated to protect against known security flaws.