CVE-2019-17010 in Firefox
Summary
by MITRE
Under certain conditions, when checking the Resist Fingerprinting preference during device orientation checks, a race condition could have caused a use-after-free and a potentially exploitable crash. This vulnerability affects Thunderbird < 68.3, Firefox ESR < 68.3, and Firefox < 71.
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Analysis
by VulDB Data Team • 01/09/2020
This vulnerability represents a critical race condition flaw in Mozilla's browser and email client implementations that could lead to arbitrary code execution through use-after-free conditions. The issue manifests specifically during device orientation checks when the Resist Fingerprinting preference is being evaluated, creating a temporal window where memory management becomes compromised. The vulnerability affects multiple Mozilla products including Thunderbird versions prior to 68.3, Firefox ESR versions prior to 68.3, and Firefox versions prior to 71, indicating a widespread impact across the Mozilla ecosystem. The race condition occurs when multiple threads attempt to access the same memory location simultaneously, with one thread freeing memory while another attempts to use it, creating a dangerous use-after-free scenario that can be exploited by malicious actors.
The technical implementation of this vulnerability stems from improper synchronization mechanisms within the orientation checking subsystem when processing fingerprinting resistance preferences. When device orientation events trigger preference validation, the code path does not adequately protect against concurrent access patterns that could result in memory deallocation before subsequent operations complete. This flaw aligns with CWE-362, which specifically addresses race conditions in concurrent programming environments where multiple threads can access shared resources without proper mutual exclusion. The vulnerability creates an exploitable crash condition that can be leveraged to execute arbitrary code, making it particularly dangerous in the context of browser-based attacks.
The operational impact of this vulnerability extends beyond simple crash conditions to potentially enable full remote code execution capabilities. Attackers can exploit this race condition to manipulate memory contents and redirect execution flow, effectively bypassing modern security mitigations such as address space layout randomization and data execution prevention. The vulnerability's exploitation requires careful timing and specific conditions, but once achieved, it provides attackers with a powerful foothold for further compromise. This aligns with ATT&CK technique T1059.007, which covers the use of scripting languages for code execution, as the use-after-free condition can be leveraged to inject and execute malicious payloads. The widespread affected versions suggest that many users would be exposed to this risk without immediate patching.
Mitigation strategies for this vulnerability require immediate deployment of patched versions across all affected Mozilla products, with particular emphasis on Firefox ESR and Thunderbird installations that may be used in enterprise environments. Organizations should implement automated patch management systems to ensure timely updates and reduce exposure windows. Additionally, browser hardening measures including disabling unnecessary features and implementing strict content security policies can provide additional defense-in-depth layers. Security teams should monitor for exploitation attempts through network traffic analysis and endpoint detection systems, as the crash conditions may be observable during exploitation attempts. The vulnerability highlights the importance of proper synchronization in multi-threaded environments and underscores the need for comprehensive testing of concurrent code paths, particularly in privacy and security-related features where race conditions can create exploitable scenarios.