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Fencer Vulns
high 7.1

CVE-2026-25536 json

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

published 2026-02-04 9 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-5335 , GHSA-345p-7cg4-v4c7

cvss
7.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm @modelcontextprotocol/sdk 1.26.0
  • Red Hat Red Hat Ansible Automation Platform 2.6 1772196222

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-25536 updated cvss 7.1

@modelcontextprotocol/sdk: @modelcontextprotocol/sdk cross-client data leak

  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-tech-preview 1772196222
    fixed: vendor fix RHSA-2026:3960
  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform 1772556678, ansible-automation-platform 1772556679, ansible-automation-platform-26 1772204398, ansible-automation-platform-26 1772381996, ansible-automation-platform-26 1772382003, ansible-automation-platform-26 1772382254, +21 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
9 mo ago

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
CISA ADP 3.1 7.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
GitHub 3.1 7.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm @modelcontextprotocol/sdk
>=1.10.0, <1.26.0
1.26.0

Affected products

  • modelcontextprotocol typescript-sdk
  • Red Hat Red Hat Ansible Automation Platform 2.6

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
  • CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.