CVE-2014-1567 in Firefox
Summary
by MITRE
Use-after-free vulnerability in DirectionalityUtils.cpp in Mozilla Firefox before 32.0, Firefox ESR 24.x before 24.8 and 31.x before 31.1, and Thunderbird 24.x before 24.8 and 31.x before 31.1 allows remote attackers to execute arbitrary code via text that is improperly handled during the interaction between directionality resolution and layout.
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Analysis
by VulDB Data Team • 11/25/2025
The CVE-2014-1567 vulnerability represents a critical use-after-free flaw in Mozilla Firefox and Thunderbird email clients that emerged from improper memory management during text directionality processing. This vulnerability resides in the DirectionalityUtils.cpp file, which handles the complex task of determining text directionality for internationalized content, particularly affecting languages that use right-to-left scripts such as Arabic and Hebrew. The flaw occurs when the application processes text that contains mixed directionality elements, creating conditions where freed memory locations are accessed after the original memory allocation has been released, leading to potential code execution.
The technical implementation of this vulnerability stems from the interaction between directionality resolution and layout computation within the browser's rendering engine. When processing text containing mixed left-to-right and right-to-left directional elements, the application's handling of these directional properties creates a scenario where memory allocated for directionality data structures becomes freed during layout processing but is subsequently accessed by subsequent operations. This memory management error follows the classic use-after-free pattern where an attacker can manipulate input text to control the freed memory's contents and redirect execution flow. The vulnerability manifests specifically during the interaction between Unicode bidirectional algorithm processing and the document layout engine, creating a pathway for arbitrary code execution through carefully crafted text input.
The operational impact of CVE-2014-1567 extends beyond typical browser exploitation scenarios as it leverages the sophisticated text processing capabilities of modern web browsers to achieve remote code execution. Attackers can craft malicious emails or web content containing specially formatted text that triggers the vulnerable code path when the application attempts to render or process the directional properties of the text. This vulnerability is particularly dangerous because it can be exploited through email clients like Thunderbird and Firefox, making it a vector for phishing attacks, malware distribution, and social engineering campaigns. The attack requires minimal user interaction beyond viewing the malicious content, as the exploitation occurs during normal text processing operations within the application's rendering pipeline.
Mitigation strategies for this vulnerability focus on immediate patch deployment and application hardening measures. The primary solution involves upgrading to patched versions of Firefox 32.0, Firefox ESR 24.8, and Thunderbird 24.8, which contain fixes that properly manage memory allocation and deallocation during directionality processing. Additionally, security hardening measures should include implementing address space layout randomization, stack canaries, and other exploit mitigations to reduce the effectiveness of potential exploitation attempts. Network security controls such as email filtering and web content restrictions can provide additional protection layers while patches are deployed. From a compliance perspective, this vulnerability aligns with CWE-416 which specifically addresses use-after-free conditions, and represents a significant concern under ATT&CK framework's technique T1203 for Exploitation for Client Execution, demonstrating how text processing vulnerabilities can be weaponized for remote code execution in email and web environments.
The vulnerability demonstrates the complexity of modern text processing systems and how seemingly benign features like internationalization support can create security risks. The interaction between Unicode bidirectional algorithm implementation and layout engine memory management creates a unique exploitation vector that highlights the importance of thorough security testing for internationalization features. Organizations should prioritize patch management for these applications and consider implementing additional security controls such as sandboxing and privilege separation to limit the impact of potential exploitation. This vulnerability also underscores the need for comprehensive security testing of text processing libraries and the importance of memory safety practices in complex software systems that handle user-supplied text data.