Uncontrolled memory allocation in MCP Kotlin SDK WebSockets
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- No fix listed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-770.
Summary
The MCP Kotlin SDK through 0.15.0 contains an uncontrolled memory allocation flaw (CWE-770) because Application.mcpWebSocket installs Ktor WebSockets without a maxFrameSize limit. A remote client can send small frame headers declaring payloads near 2 GiB over one or a few connections, forcing huge heap allocations that exhaust server memory and cause denial of service.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
The sources list no fixed version for MCP Kotlin SDK.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Vendor assessments
Timeline
- 2026-10-11 Threatist record created from CVE-2026-108714
- 2026-10-11 Alias added: GHSA-645v-p22p-m3jx
- 2026-10-12 Priority changed: MEDIUM → LOW
- 2026-10-14 CISA SSVC decision points changed
- 2026-10-14 Priority changed: LOW → MEDIUM
- 2026-11-06 Affected versions changed · Red Hat
- 2026-11-06 CVSS score added · Red Hat
References
Other 3
- 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://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
More MLflow vulnerabilities
- TI-2026-46366 Server-side request forgery in mlflow KEVCVSS 3.1CRITICAL 9.3
- TI-2023-03518 Absolute Path Traversal in mlflow/mlflow CVSS 3.1CRITICAL 10.0
- TI-2023-01113 Path Traversal: '\..\filename' in mlflow/mlflow CVSS 3.1CRITICAL 9.8
- TI-2025-31759 Redis Lua Use-After-Free may lead to remote code execution CVSS 3.1CRITICAL 10.0
- TI-2026-81527 Code execution via scorer deserialization in MLflow servers CVSS 3.1CRITICAL 9.8
- TI-2025-14028 Command Injection in mlflow/mlflow CVSS 3.1CRITICAL 10.0
Sources
- CVE-2026-108714 · CVE Program
- CVE-2026-108714 · NVD
- FIRST EPSS
- GHSA-645v-p22p-m3jx · GitHub Advisory Database · CC BY 4.0
- CVE-2026-108714 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences