CVE-2014-3756 in Mumble
Summary
by MITRE
The client in Mumble 1.2.x before 1.2.6 allows remote attackers to force the loading of an external file and cause a denial of service (hang and resource consumption) via a crafted string that is treated as rich-text by a Qt widget, as demonstrated by the (1) user or (2) channel name in a Qt dialog, (3) subject common name or (4) email address to the Certificate Wizard, or (5) server name in a tooltip.
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Analysis
by VulDB Data Team • 04/04/2022
The vulnerability identified as CVE-2014-3756 represents a critical security flaw in Mumble 1.2.x versions prior to 1.2.6, specifically targeting the client application's handling of rich-text input through Qt widgets. This vulnerability stems from insufficient input validation and sanitization mechanisms within the graphical user interface components that process user-provided data. The flaw allows remote attackers to craft malicious strings that exploit the Qt framework's rich-text parsing capabilities, creating a dangerous attack vector that can be leveraged across multiple user interface elements within the application.
The technical implementation of this vulnerability occurs when the Mumble client processes user-provided strings through Qt dialog widgets that support rich-text formatting. When an attacker supplies a crafted string containing malicious rich-text markup, the Qt widget's parser attempts to process and render this content, leading to resource exhaustion and application hanging. This occurs because the Qt framework's rich-text parser does not properly validate or sanitize input before processing, allowing malicious content to trigger infinite loops or excessive resource consumption during rendering operations. The vulnerability manifests across multiple attack vectors including user names, channel names, certificate wizard fields, and tooltip text, making it particularly dangerous as it can be triggered through various user interaction points within the application.
The operational impact of CVE-2014-3756 extends beyond simple denial of service to potentially enable more sophisticated attack scenarios. When the application hangs due to malicious rich-text processing, users experience complete service disruption, effectively preventing them from accessing the voice communication services. The resource consumption aspect can lead to system instability, particularly in environments where multiple users are simultaneously affected, potentially causing cascading failures. This vulnerability aligns with CWE-129, which addresses improper validation of input length, and CWE-20, which covers input validation issues in general. The attack pattern follows ATT&CK technique T1499.004 for network denial of service, where adversaries exploit application-level vulnerabilities to disrupt services.
Mitigation strategies for this vulnerability require immediate application updates to version 1.2.6 or later, which includes proper input sanitization and validation mechanisms. System administrators should implement network-level restrictions to prevent untrusted users from submitting content to Mumble servers, particularly in multi-tenant environments. The fix typically involves implementing proper rich-text parsing limits, input length restrictions, and sanitization routines that prevent malicious markup from being processed by Qt widgets. Additionally, organizations should consider implementing application whitelisting policies that restrict the execution of potentially vulnerable applications and ensure all user interface components properly validate and sanitize rich-text input before processing. The vulnerability demonstrates the importance of secure input handling in GUI applications and the critical need for proper validation of user-provided content in rich-text rendering contexts.