CVE-2026-52869

HIGHPre-NVD 7.17.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 57% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.1Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
7.1
EG Score
7.1(medium)
EG Risk
32(Track)
EG Risk 32/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity71% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
43%
KEV
Not listed

Published

July 15, 2026

Last Modified

July 17, 2026

Advisory Details (6)

Auto-updated Jul 15, 2026
Patch available. Sources: github_commit, github_pr, github_release, github.
github Patch Available

HTTP transports serve session requests without verifying the authenticated principal · Advisory · modelcontextprotocol/python-sdk · GitHub

https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-jpw9-pfvf-9f58
github_release Patch Available

v1.27.2

Patch available: modelcontextprotocol/python-sdk v1.27.2

https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2
github_pr Patch Available

[v1.x] Bind transport sessions to the authenticated principal

Patch available: modelcontextprotocol/python-sdk v1.27.2 (PR #2719 merged 2026-05-29)

https://github.com/modelcontextprotocol/python-sdk/pull/2719
github_pr Patch Available

[v1.x] Add subject and claims to AccessToken

Patch available: modelcontextprotocol/python-sdk v1.27.2 (PR #2690 merged 2026-05-26)

https://github.com/modelcontextprotocol/python-sdk/pull/2690
github_commit Patch Available

commit ce267b6fc515 (modelcontextprotocol/python-sdk)

Patch available: modelcontextprotocol/python-sdk v1.27.2 (contains commit ce267b6fc515)

https://github.com/modelcontextprotocol/python-sdk/commit/ce267b6fc515dc4efc1dc70b6975b16ff0feef0a
github_commit Patch Available

commit 1abcca2408a6 (modelcontextprotocol/python-sdk)

Patch available: modelcontextprotocol/python-sdk v1.27.2 (contains commit 1abcca2408a6)

https://github.com/modelcontextprotocol/python-sdk/commit/1abcca2408a6b50e10ec601181f63f9978705c00

Vendor Advisories for CVE-2026-52869(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
mcp0.9.1 ... 1.9.4 (55 versions)1.27.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 03:46 UTCEG score recompute
  2. 2026-08-30 01:22 UTCEPSS rescore
  3. 2026-08-28 21:41 UTCEPSS rescore
  4. 2026-08-28 01:51 UTCEG score recompute
  5. 2026-08-27 14:25 UTCEPSS rescore
  6. 2026-08-26 23:04 UTCEG score recompute
  7. 2026-08-26 14:46 UTCEPSS rescore
  8. 2026-08-26 02:11 UTCEG score recompute
  9. 2026-08-25 13:49 UTCEPSS rescore
  10. 2026-08-24 23:45 UTCEG score recompute
  11. 2026-08-24 10:37 UTCEG score recompute
  12. 2026-08-23 08:16 UTCEG score recompute
  13. 2026-08-23 00:19 UTCEPSS rescore
  14. 2026-08-22 06:02 UTCEG score recompute
  15. 2026-08-21 23:49 UTCEPSS rescore
  16. 2026-08-21 03:44 UTCEG score recompute
  17. 2026-08-20 22:55 UTCEPSS rescore
  18. 2026-08-20 00:13 UTCEG score recompute
  19. 2026-08-19 17:04 UTCEPSS rescore
  20. 2026-08-18 19:59 UTCEG score recompute
  21. 2026-08-18 13:48 UTCEPSS rescore
  22. 2026-08-18 02:32 UTCEG score recompute
  23. 2026-08-17 13:47 UTCEPSS rescore
  24. 2026-08-16 22:44 UTCEG score recompute
  25. 2026-08-16 14:56 UTCEPSS rescore
Show 48 more
  1. 2026-08-16 09:36 UTCEG score recompute
  2. 2026-08-16 02:14 UTCEPSS rescore
  3. 2026-08-15 07:23 UTCEG score recompute
  4. 2026-08-15 01:30 UTCEPSS rescore
  5. 2026-08-14 04:46 UTCEG score recompute
  6. 2026-08-13 22:00 UTCEPSS rescore
  7. 2026-08-13 02:26 UTCEG score recompute
  8. 2026-08-12 13:51 UTCEPSS rescore
  9. 2026-08-12 00:12 UTCEG score recompute
  10. 2026-08-11 11:05 UTCEG score recompute
  11. 2026-08-11 00:00 UTCEPSS rescore
  12. 2026-08-09 19:44 UTCEG score recompute
  13. 2026-08-09 13:46 UTCEPSS rescore
  14. 2026-08-08 04:24 UTCEG score recompute
  15. 2026-08-07 02:10 UTCEG score recompute
  16. 2026-08-06 13:47 UTCEPSS rescore
  17. 2026-08-05 23:56 UTCEG score recompute
  18. 2026-08-05 19:17 UTCEPSS rescore
  19. 2026-08-04 21:42 UTCEG score recompute
  20. 2026-08-04 15:10 UTCEPSS rescore
  21. 2026-08-04 10:39 UTCEPSS rescore
  22. 2026-08-01 14:24 UTCEG score recompute
  23. 2026-08-01 04:16 UTCEPSS rescore
  24. 2026-07-30 23:01 UTCEG score recompute
  25. 2026-07-30 16:28 UTCEPSS rescore
  26. 2026-07-30 09:53 UTCEG score recompute
  27. 2026-07-30 01:30 UTCEPSS rescore
  28. 2026-07-28 17:32 UTCEG score recompute
  29. 2026-07-28 15:37 UTCEPSS rescore
  30. 2026-07-27 15:16 UTCEG score recompute
  31. 2026-07-27 00:36 UTCEG score recompute
  32. 2026-07-26 14:54 UTCEPSS rescore
  33. 2026-07-26 11:29 UTCEG score recompute
  34. 2026-07-25 14:18 UTCEPSS rescore
  35. 2026-07-24 14:18 UTCEPSS rescore
  36. 2026-07-23 14:18 UTCEPSS rescore
  37. 2026-07-23 03:19 UTCEG score recompute
  38. 2026-07-22 14:08 UTCEPSS rescore
  39. 2026-07-21 15:25 UTCEPSS rescore
  40. 2026-07-20 17:08 UTCEPSS rescore
  41. 2026-07-19 14:31 UTCEPSS rescore
  42. 2026-07-19 14:31 UTCEPSS rescore
  43. 2026-07-19 02:37 UTCEG score recompute
  44. 2026-07-19 02:29 UTCEPSS rescore
  45. 2026-07-18 10:04 UTCEPSS rescore
  46. 2026-07-16 17:03 UTCEPSS rescore
  47. 2026-07-15 20:10 UTCEG score recompute
  48. 2026-07-15 20:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-52869?
CVE-2026-52869 is a high vulnerability published on July 15, 2026. 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.streamablehttpmanager.StreamableHTTPSessionManager route requests to existing…
When was CVE-2026-52869 disclosed?
CVE-2026-52869 was first published in the National Vulnerability Database on July 15, 2026, with the most recent update on July 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-52869 actively exploited?
CVE-2026-52869 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 57.2% of all scored CVEs.
What is the CVSS score of CVE-2026-52869?
CVE-2026-52869 has a CVSS v3 base score of 7.1 (NVD).
How do I remediate CVE-2026-52869?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-52869, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-52869

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