CVE-2019-11691 Explained : Impact and Mitigation

A use-after-free vulnerability in XMLHttpRequest (XHR) can lead to potential crashes in Thunderbird, Firefox, and Firefox ESR.

Understanding CVE-2019-11691

What is CVE-2019-11691?

This CVE involves a use-after-free vulnerability in XMLHttpRequest (XHR) when used in an event loop, potentially causing crashes in Thunderbird, Firefox, and Firefox ESR.

The Impact of CVE-2019-11691

When the XHR main thread is invoked after deallocation, it can result in exploitable crashes in affected versions of Thunderbird, Firefox, and Firefox ESR.

Technical Details of CVE-2019-11691

Vulnerability Description

The vulnerability arises from using XHR in an event loop, leading to a use-after-free scenario that can be exploited to cause crashes.

Affected Systems and Versions

Thunderbird versions prior to 60.7
Firefox versions prior to 67
Firefox ESR versions prior to 60.7

Exploitation Mechanism

The vulnerability occurs when the XHR main thread is called after deallocation, creating a potential for exploitation and crashes.

Mitigation and Prevention

Immediate Steps to Take

Update Thunderbird, Firefox, and Firefox ESR to versions 60.7, 67, and 60.7 respectively.
Avoid using XHR in an event loop until the systems are patched.

Long-Term Security Practices

Regularly update software to the latest versions to ensure security patches are applied.
Implement secure coding practices to prevent similar vulnerabilities.

Patching and Updates

Apply the latest patches provided by Mozilla to address the use-after-free vulnerability in XHR.