CVE-2019-9820 in Firefox
Summary
by MITRE
A use-after-free vulnerability can occur in the chrome event handler when it is freed while still in use. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 60.7, Firefox < 67, and Firefox ESR < 60.7.
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Analysis
by VulDB Data Team • 06/06/2024
The vulnerability identified as CVE-2019-9820 represents a critical use-after-free condition within the chrome event handler component of Mozilla's browser and email applications. This flaw manifests when memory allocated for chrome event handlers is released while still being actively referenced by the application's execution flow, creating a scenario where subsequent operations may attempt to access already freed memory locations. The vulnerability resides in the core event handling mechanisms that manage user interface interactions and system notifications within the browser environment. Such memory management errors typically arise from improper reference counting or lifecycle management of objects within the application's runtime environment. The affected software versions include Thunderbird versions prior to 60.7, Firefox versions prior to 67, and Firefox ESR versions prior to 60.7, indicating this issue spans multiple products within the Mozilla ecosystem.
The technical exploitation of this vulnerability leverages the fundamental principles of memory corruption attacks, specifically targeting the memory management subsystem of the affected applications. When a chrome event handler is freed while still in use, the memory location may be reallocated for other purposes, but if the application attempts to access the freed handler, it could result in unpredictable behavior including application crashes or potentially arbitrary code execution. This type of vulnerability falls under the CWE-416 category of Use After Free, which is classified as a serious memory safety issue. The attack surface is particularly concerning because chrome event handlers are integral to the user interface and system integration components, making them prime targets for exploitation. The vulnerability's impact extends beyond simple application instability, as it can potentially be leveraged by attackers to execute malicious code with the privileges of the affected user.
The operational implications of CVE-2019-9820 are severe given the widespread deployment of affected software across enterprise and individual user environments. Organizations relying on Firefox or Thunderbird for email services and web browsing operations face significant risk of compromise if systems remain unpatched. The vulnerability's potential for remote code execution means that attackers could exploit this flaw through malicious web content or email attachments, making it particularly dangerous in targeted attack scenarios. Security teams must consider the broader attack surface that includes not just web browsing but also email processing capabilities within Thunderbird. The vulnerability's presence in both regular Firefox releases and the Extended Support Release (ESR) versions indicates that even organizations maintaining older, stable software versions are at risk. This affects both desktop and mobile deployment scenarios where these applications are commonly used.
Mitigation strategies for CVE-2019-9820 should prioritize immediate patch deployment across all affected systems, with particular attention to enterprise environments where multiple user accounts and system configurations may be impacted. Security administrators should implement network-based protections such as content filtering and web application firewalls to prevent exploitation attempts through web-based attack vectors. The vulnerability's classification as a use-after-free condition suggests that automated memory corruption detection tools and runtime protections could help identify potential exploitation attempts, though these are not foolproof solutions. Organizations should also consider implementing additional security controls such as application whitelisting and privilege separation to limit the potential impact of successful exploitation. The ATT&CK framework categorizes this vulnerability under T1059 (Command and Scripting Interpreter) and T1068 (Exploitation for Privilege Escalation) when successfully exploited, indicating that mitigation efforts should include monitoring for suspicious process behavior and privilege escalation attempts. Regular security assessments and vulnerability scanning should be conducted to ensure all systems remain protected against this and similar memory corruption vulnerabilities.