CVE-2014-3755 in Mumble
Summary
by MITRE
The QSvg module in Qt, as used in the Mumble client 1.2.x before 1.2.6, allows remote attackers to cause a denial of service (hang and resource consumption) via a local file reference in an (1) image tag or (2) XML stylesheet in an SVG file.
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Analysis
by VulDB Data Team • 04/04/2022
The vulnerability identified as CVE-2014-3755 represents a significant denial of service weakness within the Qt framework's QSvg module, specifically affecting the Mumble client version 1.2.x prior to 1.2.6. This flaw manifests when the application processes SVG files containing maliciously crafted local file references within image tags or XML stylesheets, creating a scenario where remote attackers can manipulate the application's behavior to consume excessive system resources or cause complete application hang. The vulnerability stems from insufficient input validation and improper handling of external resource references within SVG processing components, allowing attackers to craft SVG files that trigger resource exhaustion through recursive or excessive file system access patterns.
The technical exploitation of this vulnerability occurs through the improper parsing of SVG elements that reference local files through image tags or XML stylesheets. When the Mumble client processes such malformed SVG content, the QSvg module attempts to resolve these local file references, potentially triggering infinite loops or excessive resource consumption during file system traversal operations. This behavior aligns with CWE-400, which catalogs weaknesses related to resource exhaustion, and demonstrates how improper handling of external references can lead to denial of service conditions. The vulnerability specifically targets the SVG rendering pipeline within Qt applications, where the framework's XML parser and stylesheet processing components fail to adequately validate or limit the scope of local file access.
From an operational impact perspective, this vulnerability enables remote attackers to perform denial of service attacks against Mumble clients by simply sending malicious SVG files to connected users. The consequences include complete application hang, excessive memory consumption, and potential system performance degradation that can affect the entire communication session. In a voice communication context like Mumble, this can effectively disrupt real-time conversations and collaboration, as the application becomes unresponsive to user input and network operations. The vulnerability is particularly concerning because it can be exploited through legitimate file sharing channels within the application, making it difficult to detect and prevent without proper input sanitization.
The mitigation strategies for CVE-2014-3755 primarily focus on updating to Mumble version 1.2.6 or later, which includes patches that properly validate SVG file content and implement resource limits for external reference resolution. Organizations should also implement additional security measures such as SVG file validation at network boundaries, sandboxed processing of user-generated content, and monitoring for unusual resource consumption patterns. From an ATT&CK framework perspective, this vulnerability maps to technique T1499.004, which covers network denial of service attacks, and T1059.007, involving scripting through command-line interpreters, as the exploitation involves processing of malicious content through legitimate application interfaces. The fix implemented by the Mumble developers likely includes enhanced input validation, proper resource limiting for file system operations, and stricter enforcement of XML parsing rules to prevent recursive or excessive resource consumption during SVG processing operations.