RMCP is an official Rust SDK for the Model Context Protocol. Prior to 2.0.0, the rmcp crate's stateful Streamable HTTP server in crates/rmcp/src/transport/streamable_http_server/tower.rs allows an unauthenticated client to send a well-formed JSON-RPC POST that is not an initialization request, or an initialization request with a mismatched protocol header, causing StreamableHttpService::handle_post to call LocalSessionManager.create_session before validating the message. An early validation failure returns without removing the inserted LocalSessionHandle from LocalSessionManager.sessions, permanently retaining session and channel state for the server process lifetime. Repeated requests can grow the shared session table without bound, degrade legitimate-client latency through lock contention, exhaust memory, and terminate the server. This issue is fixed in version 2.0.0.
CVE-2026-63128
“—” beside the score: it is equal to the CVSS score beside it.
Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-16. A secondary CVSS source baseline 7.5; sources differ by 0.0.
Also known asEUVD-2026-80823 (ENISA EUVD) · GHSA-9pj6-vhgr-3mwh (GitHub Security Advisories)Source: ENISA EUVD
- CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHmedium confidence
- EG Risk
- 50EG Risk 50/100
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)Severity75% × 45%Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation40% × 40%EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.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 public PoC (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
- 0.5%
- EPSS %ILE
- 45th
- 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 (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.5% 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 low or medium mission impact; Track* at high (mission-essential systems).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 low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation public PoC (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
September 16, 2026
Last Modified
September 30, 2026
Advisory Details (4)
Auto-updated Sep 16, 2026Unauthenticated permanent session-table leak in rmcp Streamable HTTP server transport leads to remote denial-of-service · Advisory · modelcontextprotocol/rust-sdk · GitHub
Affected: 1.4.0 (
https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-9pj6-vhgr-3mwhrmcp-v2.0.0
Patch available: modelcontextprotocol/rust-sdk rmcp-v2.0.0
https://github.com/modelcontextprotocol/rust-sdk/releases/tag/rmcp-v2.0.0fix: prevent streamable HTTP session leak
Patch available: modelcontextprotocol/rust-sdk rmcp-macros-v3.0.0-beta.1 (PR #934 merged 2026-06-27)
https://github.com/modelcontextprotocol/rust-sdk/pull/934commit dfa7fd6f9309 (modelcontextprotocol/rust-sdk)
Patch available: modelcontextprotocol/rust-sdk rmcp-macros-v3.0.0-beta.1 (contains commit dfa7fd6f9309)
https://github.com/modelcontextprotocol/rust-sdk/commit/dfa7fd6f9309deab60bea230b041be9a3fcda846Vendor Advisories for CVE-2026-63128(3)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:80765Red Hat Product SecurityHigh
Red Hat Security Advisory: goose security update
- RHSA-2026:80764Red Hat Product SecurityHigh
Red Hat Security Advisory: goose security update
- GHSA-9pj6-vhgr-3mwhGitHub Security AdvisoriesHigh
RMCP: Unauthenticated permanent session-table leak in rmcp Streamable HTTP server transport leads to remote denial-of-service
Patch Availability(1)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| rust | rmcp @ 2.0.0 (fixes < 2.0.0) | — | 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)
crates.io(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| rmcp | — |
| — |
Weakness Classification(3)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 50× 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 16:35 UTCEPSS rescoreEPSS 0.5% · 45th percentile
- 2026-11-01 07:41 UTCGHSA enrichmentGHSA-9pj6-vhgr-3mwh · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-11-01 07:41 UTCEG score recompute
- 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.5% · 45th percentile
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.5% · 45th percentile
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.5% · 45th percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.5% · 45th percentile
- 2026-10-27 18:49 UTCEG score recompute
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-10-25 14:13 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-20 09:18 UTCEG score recompute
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-18 03:23 UTCEG score recompute
- 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.6% · 48th percentile
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- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-13 12:04 UTCEG score recompute
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-12 15:49 UTCEG score recompute
- 2026-10-11 19:33 UTCEG score recompute
- 2026-10-11 16:48 UTCEG score recompute
- 2026-10-11 14:10 UTCEG score recompute
- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-11 11:31 UTCEG score recompute
- 2026-10-10 22:43 UTCEG score recompute
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-09 21:06 UTCEG score recompute
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-08 20:34 UTCEG score recompute
- 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-08 07:53 UTCEG score recompute
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-06 19:38 UTCEG score recompute
- 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-05 19:23 UTCEG score recompute
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-05 07:10 UTCEG score recompute
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-03 18:56 UTCEG score recompute
- 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-02 18:48 UTCEG score recompute
- 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-02 06:35 UTCEG score recompute
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-30 18:08 UTCEG score recompute
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-30 00:53 UTCEG score recompute
- 2026-09-29 09:09 UTCEG score recompute
- 2026-09-28 20:58 UTCEG score recompute
- 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-27 20:49 UTCEG score recompute
- 2026-09-26 20:40 UTCEG score recompute
- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-09-26 08:34 UTCEG score recompute
- 2026-09-24 19:40 UTCEG score recompute
- 2026-09-23 19:31 UTCEG score recompute
- 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-09-22 19:18 UTCEG score recompute
- 2026-09-22 07:12 UTCEG score recompute
- 2026-09-21 07:04 UTCEG score recompute
- 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-09-19 18:43 UTCEG score recompute
- 2026-09-19 06:38 UTCEG score recompute
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 44th percentile
- 2026-09-18 06:24 UTCEG score recompute
- 2026-09-16 15:20 UTCEG score recompute
- 2026-09-16 14:51 UTCEG score recomputeFirst assessed: 7.5 HIGH
- 2026-09-16 14:50 UTCMITRE cvelistV5first tracked
Related CVEs(same product + same CWE)
Same product
3 showncrates.io:rmcp
Frequently asked(5)
What is CVE-2026-63128?
When was the CVE record for CVE-2026-63128 published?
Is CVE-2026-63128 actively exploited?
What is the CVSS score of CVE-2026-63128?
How do I remediate CVE-2026-63128?
Dependency Blast Radius
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