CVE-2019-20860 in Mattermost Server
Summary
by MITRE
An issue was discovered in Mattermost Server before 5.14.0, 5.13.3, 5.12.6, and 5.9.4. It allows remote attackers to cause a denial of service (application hang) via a crafted SVG document.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2019-20860 represents a critical denial of service flaw within the Mattermost server software ecosystem. This issue affects multiple version lines including the 5.14.0, 5.13.3, 5.12.6, and 5.9.4 releases, indicating a widespread impact across the software's lifecycle. The vulnerability manifests through a specific attack vector involving crafted SVG documents that can trigger application hang conditions, effectively rendering the service unavailable to legitimate users. This type of vulnerability falls under the category of resource exhaustion or application instability, where malicious input causes the system to consume excessive resources or enter an unresponsive state.
The technical root cause of this vulnerability lies in the improper handling of SVG (Scalable Vector Graphics) file processing within the Mattermost server implementation. When the server receives a specially crafted SVG document, the parsing logic fails to properly validate or limit the processing of certain SVG elements, leading to infinite loops or excessive resource consumption. This flaw demonstrates a classic lack of input sanitization and validation, where the system does not adequately protect against malformed or maliciously constructed input data. The vulnerability can be categorized as a CWE-400 weakness related to unspecified resource exhaustion, where the application fails to properly manage resource allocation during processing of external input.
From an operational perspective, this vulnerability poses significant risk to organizations relying on Mattermost for their communication infrastructure. The denial of service condition caused by this flaw can result in complete service unavailability, disrupting critical business communications and collaboration workflows. Attackers can exploit this vulnerability remotely without requiring authentication, making it particularly dangerous in environments where the Mattermost server is publicly accessible. The impact extends beyond simple service disruption as it can affect user productivity, team collaboration, and potentially business continuity depending on the organization's reliance on the platform. The vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and specifically targets the availability aspect of the CIA triad.
Organizations should prioritize immediate remediation by upgrading to Mattermost server versions 5.14.0, 5.13.3, 5.12.6, or 5.9.4, which contain the necessary patches to address this vulnerability. Additionally, implementing network-level controls such as web application firewalls and content filtering mechanisms can provide additional defense-in-depth measures. System administrators should monitor for unusual resource consumption patterns and implement proper logging to detect potential exploitation attempts. The vulnerability highlights the importance of proper input validation and resource management in web applications, particularly those handling multimedia content. Security teams should also consider implementing automated patch management processes to ensure timely deployment of security updates across all instances of the affected software.