CVE-2026-52869

HIGHPre-NVD 7.17.1
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This high-severity CVE scores 7.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (43rd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
7.1EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 7.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
7.1HIGHmedium confidence
EG Risk
32
EG Risk 32/100

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 (value × EchelonGraph’s weight)
Severity71% × 45%
The EG Score, 7.1 of 10.
Exploitation0.5% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
43rd
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

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 advisoryMentions a patch (unverified)

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 pull request 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 pull request 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 rangeFix by version rangeDependents
mcp0.9.1 ... 1.9.4 (55 versions)
  • every version up to 1.27.2: fixed in 1.27.2
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 33× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 123 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 23 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  3. 2026-10-12 15:58 UTCEG score recompute
  4. 2026-10-11 19:41 UTCEG score recompute
  5. 2026-10-11 16:56 UTCEG score recompute
  6. 2026-10-11 14:19 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  9. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  10. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  11. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  12. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  13. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  14. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  15. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  16. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  17. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  18. 2026-10-01 12:36 UTCEG score recompute
  19. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  20. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  21. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  22. 2026-09-28 08:41 UTCEG score recompute
  23. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  24. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  25. 2026-09-26 00:27 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
Show 75 more
  1. 2026-09-24 08:47 UTCEG score recompute
  2. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  3. 2026-09-23 03:14 UTCEG score recompute
  4. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  5. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  6. 2026-09-18 04:43 UTCEG score recompute
  7. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  8. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  9. 2026-09-13 23:11 UTCEG score recompute
  10. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  11. 2026-09-13 07:12 UTCEG score recompute
  12. 2026-09-11 21:44 UTCEG score recompute
  13. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  14. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  15. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  16. 2026-09-08 00:42 UTCEG score recompute
  17. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  18. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  19. 2026-09-05 20:48 UTCEG score recompute
  20. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  21. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  22. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  23. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  24. 2026-08-31 06:01 UTCEG score recompute
  25. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  26. 2026-08-30 03:46 UTCEG score recompute
  27. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  28. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  29. 2026-08-28 01:51 UTCEG score recompute
  30. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  31. 2026-08-26 23:04 UTCEG score recompute
  32. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  33. 2026-08-26 02:11 UTCEG score recompute
  34. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  35. 2026-08-24 23:45 UTCEG score recompute
  36. 2026-08-24 10:37 UTCEG score recompute
  37. 2026-08-23 08:16 UTCEG score recompute
  38. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  39. 2026-08-22 06:02 UTCEG score recompute
  40. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  41. 2026-08-21 03:44 UTCEG score recompute
  42. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  43. 2026-08-20 00:13 UTCEG score recompute
  44. 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  45. 2026-08-18 19:59 UTCEG score recompute
  46. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  47. 2026-08-18 02:32 UTCEG score recompute
  48. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  49. 2026-08-16 22:44 UTCEG score recompute
  50. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  51. 2026-08-16 09:36 UTCEG score recompute
  52. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  53. 2026-08-15 07:23 UTCEG score recompute
  54. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  55. 2026-08-14 04:46 UTCEG score recompute
  56. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  57. 2026-08-13 02:26 UTCEG score recompute
  58. 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  59. 2026-08-12 00:12 UTCEG score recompute
  60. 2026-08-11 11:05 UTCEG score recompute
  61. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  62. 2026-08-09 19:44 UTCEG score recompute
  63. 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  64. 2026-08-08 04:24 UTCEG score recompute
  65. 2026-08-07 02:10 UTCEG score recompute
  66. 2026-08-06 13:47 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  67. 2026-08-05 23:56 UTCEG score recompute
  68. 2026-08-05 19:17 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  69. 2026-08-04 21:42 UTCEG score recompute
  70. 2026-08-04 15:10 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  71. 2026-08-04 10:39 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  72. 2026-08-01 14:24 UTCEG score recompute
  73. 2026-08-01 04:16 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  74. 2026-07-30 23:01 UTCEG score recompute
  75. 2026-07-30 16:28 UTCEPSS rescoreEPSS 0.3% · 24th percentile

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Frequently asked(5)

What is CVE-2026-52869?
CVE-2026-52869 is a high-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-52869 published?
The CVE record for CVE-2026-52869 was published on July 15, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of July 17, 2026; the record at its source may have been updated since.
Is CVE-2026-52869 actively exploited?
CVE-2026-52869 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (43rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-52869?
CVE-2026-52869 has a CVSS base score of 7.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-52869?
A fix for CVE-2026-52869 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-52869 are linked in the Vendor Advisories panel on this page.

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