The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.8.0 until 1.30.0 and 2.2.0, streamable_http_client, streamablehttp_client, sse_client, ClientSessionGroup, OAuth, and create_mcp_http_client client paths enable follow_redirects and follow redirects to a different origin, forwarding caller-supplied custom credential headers and, for 307 or 308 responses, the request body. An attacker who can influence a trusted endpoint's redirect destination can receive that material. This issue is fixed in versions 1.30.0 and 2.2.0.
CVE-2026-116685
“—” beside the score: it is equal to the CVSS score beside it.
Score 5.9 from GitHub Security Advisory (severity: MODERATE) published 2026-10-27. A secondary CVSS source baseline 5.9; sources differ by 0.0.
Also known asEUVD-2026-111367 (ENISA EUVD) · GHSA-5h93-6whr-6q8j (GitHub Security Advisories)Source: ENISA EUVD
- Lower severity and no public exploit yet
A fix is available — apply it.
- CVSS v3
- 5.9
- EG Score
- 5.9MEDIUMhigh confidence
- EG Risk
- 27EG Risk 27/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity59% × 45%Impact severity (EG Severity): CVSS 5.9 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.4% × 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 every mission impact level.Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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
- 0.4%
- EPSS %ILE
- 34th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.9): severity, escalated by confirmed exploitation. This CVE's 5.9 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.9 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (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
October 27, 2026
Last Modified
October 30, 2026
Advisory Details (7)
Auto-updated Oct 27, 2026HTTP client transports followed cross-origin redirects carrying custom headers and bodies · Advisory · modelcontextprotocol/python-sdk · GitHub
https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-5h93-6whr-6q8jv2.2.0
Patch available: modelcontextprotocol/python-sdk v2.2.0
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0v1.30.0
Patch available: modelcontextprotocol/python-sdk v1.30.0
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0[v1.x] Follow redirects only within the MCP endpoint's origin
Patch available: modelcontextprotocol/python-sdk v1.30.0 (PR #3448 merged 2026-09-05)
https://github.com/modelcontextprotocol/python-sdk/pull/3448Follow redirects only within the MCP endpoint's origin
Patch available: modelcontextprotocol/python-sdk v2.2.0 (PR #3397 merged 2026-09-04)
https://github.com/modelcontextprotocol/python-sdk/pull/3397commit c6762e821c52 (modelcontextprotocol/python-sdk)
Patch available: modelcontextprotocol/python-sdk v2.2.0 (contains commit c6762e821c52)
https://github.com/modelcontextprotocol/python-sdk/commit/c6762e821c527925f0b617db216d00fbd1d0bf99commit 210633574556 (modelcontextprotocol/python-sdk)
Patch available: modelcontextprotocol/python-sdk v1.30.0 (contains commit 210633574556)
https://github.com/modelcontextprotocol/python-sdk/commit/2106335745563b2321b8c73fef2c12903d00aa6eVendor Advisories for CVE-2026-116685(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Patch Availability(2)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| pip | mcp @ 2.2.0 (fixes >= 2.0.0, < 2.2.0) | — | ghsa |
| pip | mcp @ 1.30.0 (fixes >= 1.8.0, < 1.30.0) | — | ghsa |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| mcp | 2.0.0, 2.0.1, 2.1.0, 2.1.1 |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 13× in last 7d / 13× 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.
- 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-11-01 07:59 UTCGHSA enrichmentGHSA-5h93-6whr-6q8j · GitHub severity MODERATE · GitHub CVSS 5.9
- 2026-11-01 07:59 UTCEG score recompute
- 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-30 16:28 UTCEG score recompute
- 2026-10-30 15:20 UTCEG score recompute
- 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-27 20:26 UTCEG score recompute
- 2026-10-27 20:01 UTCENISA EUVD ID recordedEUVD-2026-111367 · Source: ENISA EUVD
- 2026-10-27 19:35 UTCEG score recomputeFirst assessed: 5.9 MEDIUM
- 2026-10-27 19:34 UTCMITRE cvelistV5first tracked
Related CVEs(same product + same CWE)
Same product
9 shownPyPI:mcp
Frequently asked(5)
What is CVE-2026-116685?
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Dependency Blast Radius
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