Quick answers
- Is CVE-2026-109527 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-109527 being exploited in the wild.
- How severe is CVE-2026-109527?
- High severity, with a CVSS score of 7.5, published 14 October 2026.
- Which products and versions are affected?
- Modelcontextprotocol Model Context Protocol Python SDK before 1.29.1, and 2.0.0a1 through 2.0.1.
- Is there a fix for CVE-2026-109527?
- Yes: fixed in 1.29.1, 2.1.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-109527 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-109527?
- Check whether you run Modelcontextprotocol Model Context Protocol Python 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.
How to fix
- Fixed in: 1.29.1, 2.1.0
Technical details
The Streamable HTTP session manager, SSE message endpoint, and OAuth authorization-server routes buffer complete HTTP request bodies without enforcing a size limit. An unauthenticated remote attacker able to reach these endpoints can send a large declared or streamed request body that consumes multiple times the declared body size in process memory, leading to memory exhaustion or process termination. Stdio-only servers and deployments with upstream request-size limits are unaffected; the vulnerability is fixed in mcp 1.29.1 and 2.1.0.
Affected products
- modelcontextprotocol Model Context Protocol Python SDK before 1.29.1, and 2.0.0a1 through 2.0.1
Timeline
- 2026-10-14: disclosed