CVE-2026-52869: The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP)

Q: How do I fix CVE-2026-52869?

mcp python sdk: upgrade to 1.27.2. Exact commands for each OS are on this page.

Q: Is CVE-2026-52869 being exploited?

CVE-2026-52869 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-52869 affect?

CVE-2026-52869 affects mcp python sdk. Severity is high (CVSS 7.1). The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to 1.27.2, the SSE and stateful Streamable HTTP transports mcp.server.sse.SseServerTransport and mcp.server.streamable_http_manage

Routine

HIGH 7.1UPGRADE

CVE-2026-52869 is a high-severity flaw (CVSS 7.1) affecting mcp python sdk. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to 1.27.2, the SSE and stateful Streamable HTTP transports mcp.server.sse.SseServerTransport and mcp.server.streamable_http_manager.StreamableHTTPSessionManager route requests to existing sessions using only the session_id query parameter or Mcp-Session-Id header without verifying the authenticated principal that created the session, allo

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.1 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.5% (top 56%)
CISA exploited list	No
Weakness	CWE-639
Published	2026-07-15
Last modified	2026-10-24

Publisher (CNA): GitHub, Inc. · Vendor: lfprojects

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-15 20:17 UTCPublished CVE record published
2026-10-24 21:10 UTCUpdated Record last modified

lfprojects mcp python sdk UPGRADE

Affected: < 1.27.2

Fixed in: 1.27.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy mcp-python-sdk || rpm -q mcp-python-sdk || mcp-python-sdk --version

2. UPGRADE to 1.27.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mcp-python-sdk

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mcp-python-sdk

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-52869?

mcp python sdk: upgrade to 1.27.2. Exact commands for each OS are on this page.

Is CVE-2026-52869 being exploited?

CVE-2026-52869 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-52869 affect?

CVE-2026-52869 affects mcp python sdk. Severity is high (CVSS 7.1). The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to 1.27.2, the SSE and stateful Streamable HTTP transports mcp.server.sse.SseServerTransport and mcp.server.streamable_http_manage

How urgent is CVE-2026-52869?

Priority 36/100. High severity

Software pages

Python vulnerabilities · PyPI packages vulnerabilities

Related CVEs

CVE-2026-52870 HIGH 7.6 UPGRADE The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP)
CVE-2026-59950 HIGH 8.1 UPGRADE The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP)

References

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