7.1

CVE-2026-52869: lfprojects mcp_python_sdk

CVSS: 7.1v3.1HighAnalyzed
AliasesGHSA-jpw9-pfvf-9f58PYSEC-2026-3482CGA-5grw-wmrx-hp7r
Published 15-07-2026Last modified 16-07-2026
Open JSON

Vulnerability summary

CVE-2026-52869 is a high (CVSS 7.1) vulnerability in lfprojects mcp_python_sdk. EPSS estimates a 0.53% chance of exploitation in the next 30 days, higher than 44% of scored vulnerabilities.

Overall risk
29/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.1/10
010
High · v3.1 (CVE.org)
EPSS score
0.53%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Related 1
CGA-RMX9-94G8-226F

Timeline

  1. 15-07-2026
    PublishedVulnerability first disclosed.
  2. 16-07-2026
    Last modifiedVulnerability information updated.

Description

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, allowing a different bearer-token-authenticated client with a known session ID to inject JSON-RPC messages into that session. This issue is fixed in version 1.27.2.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.53%

Chance of exploitation in the next 30 days

Percentile

44%

Versus all other CVEs

30-day change

0.00 pp

From 0.53% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.53%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard3 products
  • kserve-huggingfaceserver-cuda-13.3All versions (No fix recorded) | < 0.21.0-r4
  • litellm< 1.91.2-r2 | < 1.93.0-r0
  • semgrep< 1.172.0-r1
Lfprojects1 product
Modelcontextprotocol1 product
PyPI1 product
  • mcp< 1.27.2
Wolfi1 product
  • semgrep< 1.172.0-r1

5 vendors · 7 products

References

11 links
Show all 11 references