Vulnerability · Published Oct 11, 2026 · Assigned by VulnCheck
CVE-2026-108714MCP Kotlin SDK through 0.15.0 Memory Exhaustion via Application.mcpWebSocket
High 7.5
In plain English
A high-severity resource allocation without limits in kotlin-sdk from modelcontextprotocol. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 30% of all known vulnerabilities).
Official description
MCP Kotlin SDK through 0.15.0 contains an uncontrolled memory allocation vulnerability that allows remote clients to exhaust server memory because Application.mcpWebSocket installs Ktor WebSockets without a maxFrameSize limit. Attackers can send small frame headers declaring payloads near 2 GiB over one or a few connections, forcing huge heap allocations and causing denial of service.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| modelcontextprotocol | kotlin-sdk | 0 – through 0.15.0 |
Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://hackmd.io/@haind/mcp-kotlin-sdk-websocket-frame-allocation-dos third-party-advisory
- https://github.com/modelcontextprotocol/kotlin-sdk/blob/0.15.0/kotlin-sdk-server/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/server/WebSocketMcpKtorServerExtensions.kt#L41-L63 technical-description
- https://github.com/modelcontextprotocol/kotlin-sdk/blob/0.15.0/kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/shared/WebSocketMcpTransport.kt#L60-L85 technical-description
- https://github.com/modelcontextprotocol/kotlin-sdk product
- VulnCheck Advisory: MCP Kotlin SDK through 0.15.0 Memory Exhaustion via Application.mcpWebSocket third-party-advisory