CVE-2026-63128Public exploitNetwork attack vector

Unauthenticated server termination via leaked session entries

Published Sep 16, 2026 · Updated Sep 16, 2026

Resource exhaustion in Model Context Protocol Rust SDK before 2.0.0 allows remote attackers to terminate servers via crafted JSON-RPC POSTs. StreamableHttpService::handle_post creates a LocalSessionHandle before validating initialization messages, then returns on validation failure without removing the entry from LocalSessionManager.sessions. No authentication or user interaction is required; repeated requests permanently grow the shared table, increase lock contention, exhaust process memory, and interrupt every hosted session.

CVSS severity7.5
High
EPSS probabilityUnavailable
No score available in this record
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Model Context Protocol Rust SDK before 2.0.0 allows remote attackers to terminate servers via crafted JSON-RPC POSTs. StreamableHttpService::handle_post creates a LocalSessionHandle before validating initialization messages, then returns on validation failure without removing the entry from LocalSessionManager.sessions. No authentication or user interaction is required; repeated requests permanently grow the shared table, increase lock contention, exhaust process memory, and interrupt every hosted session.

The record

CVE
CVE-2026-63128
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
Model Context Protocol
Product
Rust SDK
Classifications
CWE-772, CWE-400, CWE-401, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Model Context Protocol · Rust SDKversion=< 2.0.0

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-772Missing Release of Resource after Effective Lifetime
CWE-400Uncontrolled Resource Consumption
CWE-401Missing Release of Memory after Effective Lifetime
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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