CVE-2026-71439 in Mermaid
Summary
by MITRE • 08/07/2026
Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. From version 11.6.0 until 11.16.1, Mermaid Radar Diagrams allow arbitrary large values for the ticks parameter, which can cause high CPU usage and freeze the rendering webpage or JavaScript process for long periods of time, potentially until the process is killed from memory exhaustion. This issue is fixed in version 11.16.1.
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Analysis
by VulDB Data Team • 08/07/2026
Mermaid radar diagrams contain a critical performance vulnerability that enables denial of service attacks through excessive computational resource consumption. The flaw exists in versions 11.6.0 through 11.16.1 where the ticks parameter accepts arbitrarily large numerical values without proper bounds checking or validation. This parameter controls the number of radial grid lines and labels displayed in radar charts, and when set to extremely high values such as millions or billions, the rendering engine must process an exponentially increasing number of calculations.
The technical implementation suffers from a lack of input sanitization and resource limitation mechanisms within the diagram parsing and rendering pipeline. When users provide large tick values, the JavaScript engine enters into computationally intensive loops that calculate positions, draw grid lines, and render labels for each individual tick mark. This creates a resource exhaustion scenario where CPU cycles become consumed at an unsustainable rate, leading to complete application freezing or process termination due to memory constraints.
This vulnerability directly maps to CWE-770, which addresses allocation of resources without limits or proper checking, and represents a classic example of resource exhaustion attack patterns found in the MITRE ATT&CK framework under the technique of resource exhaustion. The impact extends beyond simple performance degradation to complete system unresponsiveness, potentially affecting web applications that integrate Mermaid for dynamic diagram generation. Attackers can exploit this by crafting malicious input parameters or manipulating user-controlled data sources that feed into the diagram rendering process.
The fix implemented in version 11.16.1 introduces proper parameter validation and establishes reasonable upper limits for the ticks parameter to prevent excessive computational load. Organizations should immediately upgrade to this patched version or implement input sanitization measures if upgrading is not immediately possible. Additionally, implementing rate limiting and resource monitoring on systems that process user-generated Mermaid diagrams can provide defense-in-depth protection against similar vulnerabilities in other components of the application stack.