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.
Fix
Nothing published yet: no patch, vendor advisory or mitigation reference on NVD, no vendor advisory in the News for this CVE, not in CISA's KEV, no fixed package version. BaselineWatch does not guess at one.
Change history 2
- StatusReceived → DeferredNVD modified 2026-10-16 19:18
- First seenCVSS 8.7NVD modified 2026-10-14 14:17
Affected (CPE criteria) 0
NVD has not attached CPE configurations yet.
References 5
- https://github.com/modelcontextprotocol/kotlin-sdk
- 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
- 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
- https://hackmd.io/@haind/mcp-kotlin-sdk-websocket-frame-allocation-dos
- https://www.vulncheck.com/advisories/mcp-kotlin-sdk-through-0.15.0-memory-exhaustion-via-application-mcpwebsocket