# CVE-2026-108714: MCP Kotlin SDK uncontrolled memory allocation in WebSocket

Source: https://junglewise.ai/threats/cve-2026-108714-mcp-kotlin-sdk-through-0-15-0-contains-an-uncontrolled-memory  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-11. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-108714 · Severity: high · CVSS 7.5 · Published 2026-10-11

The MCP Kotlin SDK is a framework for building Model Context Protocol servers and clients in Kotlin. A vulnerability in the WebSocket transport allows remote attackers to send specially crafted frame headers declaring gigabyte-scale payloads, forcing the server to allocate massive amounts of heap memory and crash, resulting in a denial of service.

Vendors: [Anthropic](https://junglewise.ai/threats/vendors/anthropic).

## Quick answers

**Is CVE-2026-108714 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-108714 being exploited in the wild.

**How severe is CVE-2026-108714?** High severity, with a CVSS score of 7.5, published 11 October 2026.

**Which products and versions are affected?** Anthropic MCP Kotlin SDK through 0.15.0.

**Is there a fix for CVE-2026-108714?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-108714 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-108714?** Check whether you run Anthropic MCP Kotlin SDK at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The WebSocketMcpTransport class in MCP Kotlin SDK through 0.15.0 fails to configure a maxFrameSize limit on Ktor WebSocket sessions, allowing attackers to declare frame payloads near 2 GiB. An unauthenticated remote attacker can send small frame headers with inflated payload size declarations over one or a few network connections, triggering unbounded heap allocations that exhaust server memory and cause denial of service.

## Affected products

- Anthropic MCP Kotlin SDK through 0.15.0

## Timeline

- 2026-10-11: disclosed

## References

- [https://github.com/modelcontextprotocol/kotlin-sdk](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](https://github.com/modelcontextprotocol/kotlin-sdk/blob/0.15.0/kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/shared/WebSocketMcpTransport.kt)