CVE-2026-25536 | @modelcontextprotocol/sdk has cross-client data leak via shared server/transport instance reuse

MCP TypeScript SDK is the official TypeScript SDK for Model Context Protocol servers and clients. From version 1.10.0 to 1.25.3, cross-client response data leak when a single McpServer/Server and transport instance is reused across multiple client connections, most commonly in stateless StreamableHTTPServerTransport deployments. This issue has been patched in version 1.26.0.

Published: 2026-02-04 Last update: 2026-03-18 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-25536 is rated Low Risk (30.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.03%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-25536

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-02-05 — 0.03% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-25536

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.1 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 4.2 [email protected]

Weakness enumeration for CVE-2026-25536

GitHub Security Advisory for CVE-2026-25536

GHSA-345p-7cg4-v4c7 · Severity: high · Ecosystem: npm — @modelcontextprotocol/sdk has cross-client data leak via shared server/transport instance reuse

OS Trackers for CVE-2026-25536

vendor priority summary link
redhat high — https://access.redhat.com/security/cve/CVE-2026-25536

Affected software / configurations for CVE-2026-25536

Vendor Product Version Raw CPE
lfprojects mcp_typescript_sdk >= 1.10.0, < 1.26.0 cpe:2.3:a:lfprojects:mcp_typescript_sdk:*:*:*:*:*:*:*:*

References for CVE-2026-25536

cvelogic Threat Intelligence