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CVE-2026-111770

7.7 highEPSS 0.4%Fix available

High (7.7). EPSS 0.4% estimated probability of exploitation activity in the next 30 days. Fixed in @modelcontextprotocol/server 2.3.0.

On this page
The Model Context Protocol TypeScript SDK provides TypeScript client and server implementations of the Model Context Protocol. From 2.0.0 until 2.3.0 in @modelcontextprotocol/server, applications that shared one stateless HTTP transport or one McpServer or Server instance among multiple clients could deliver responses and notifications to the wrong client. The affected surface is an MCP server reached over HTTP by multiple clients. The trigger is reuse of one stateless transport or server instance. Messages were associated with a connection using only the JSON-RPC request identifier. SDK clients start request identifiers at zero, so collisions occur in normal operation. Cross-client delivery exposes one client's responses and notifications to another client. The issue requires an HTTP endpoint reachable by more than one client and an application that constructs the server or transport once at startup instead of once per request or session. stdio servers and factory-created per-call servers are not affected. Upgrading causes reused instances to fail and therefore requires an application code change. This issue is fixed in @modelcontextprotocol/server 2.3.0.

Severity

CVSS 3.1

7.7 high
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H
EPSS
0.4% estimated probability of exploitation activity in the next 30 days; 31st percentile. Scored 2026-11-10. A forecast for this CVE across the internet, not for your own systems.
CISA's assessment (SSVC)
Exploitation: none · Automatable: no · Technical impact: partial, assessed 2026-11-05. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
CWE
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition)
OWASP Top 10
A06:2025 Insecure Design
Published
NVD analysis
Awaiting analysis
Record from
the NVD, synced

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Affected

Versions

From the CNA's record in the CVE List.

ProductAffected
modelcontextprotocol typescript-sdk< 1.32.0
@modelcontextprotocol server>= 2.0.0, < 2.3.0

Packages (OSV)

AdvisoryEcosystemPackageAffectedFixed in
GHSA-jm63-cq47-j5jpnpm@modelcontextprotocol/server>=2.0.0 <2.3.02.3.0

Red Hat

Red Hat rates this Moderate.

Red Hat's statement

This vulnerability is evaluated as having a Moderate impact because exploitation depends on an architectural condition where a service reuses a shared server instance across concurrent connections instead of generating per-request handlers. In deployments utilizing standard input/output communication channels or per-call factory implementations, this condition cannot be triggered. Although concurrent HTTP endpoints with shared instances allow unauthorized recipients to receive message payloads meant for other callers, this architectural dependency limits the operational risk.

Red Hat's mitigation

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Contains Red Hat Security Data © Red Hat, Inc., licensed under CC BY 4.0. Source: https://access.redhat.com/security/data. Modified: reformatted. Red Hat's page for CVE-2026-111770.

Attack patterns (CAPEC)

  • CAPEC-26 Leveraging Race Conditions Likelihood: High · Severity: High
  • CAPEC-29 Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions Likelihood: High · Severity: High

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.

References

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