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Fencer Intel
medium 6.5

CVE-2026-111769 json

Model Context Protocol TypeScript SDK: HTTP client transports and OAuth requests followed cross-origin redirects and re-sent custom headers and request bodies

published 20d ago modified 7h ago also EUVD-2026-117802 , GHSA-6prh-2h8m-c8cw

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

The Model Context Protocol TypeScript SDK provides TypeScript client and server implementations of the Model Context Protocol. Prior to 1.32.0 in @modelcontextprotocol/sdk and from 2.0.0 until 2.3.0 in @modelcontextprotocol/client, the HTTP client transports and OAuth client requests followed redirects to a different origin while retaining custom request headers and, for HTTP 307 or 308 responses, request bodies. The affected surfaces are StreamableHTTPClientTransport, SSEClientTransport, and OAuth client functions such as auth(). The trigger is an HTTP redirect to another origin. Custom headers and mcp-session-id can be re-sent to the redirected origin. HTTP 307 and 308 redirects can also re-send the request body. OAuth request bodies can contain refresh_token and client_secret values. Current runtimes already strip the Authorization header across origins. stdio clients do not use the affected HTTP path. A malicious or compromised MCP or authorization server could therefore receive API keys, session identifiers, OAuth refresh tokens, or OAuth client secrets. Restoring unrestricted redirect following after upgrading restores the exposure. This issue is fixed in @modelcontextprotocol/sdk 1.32.0 and @modelcontextprotocol/client 2.3.0.

Patch / fix

  • npm @modelcontextprotocol/sdk 1.32.0
  • npm @modelcontextprotocol/client 2.3.0

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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-2026-111769 updated cvss 6.5

@modelcontextprotocol/sdk: @modelcontextprotocol/client: Model Context Protocol TypeScript SDK: Sensitive information disclosure via cross-origin redirects

  • Red Hat Hardened Images grafana13.1 13.1.8-0.6.hum1, grafana13.2 13.2.4-0.6.hum1, grafana12.4 12.4.13-0.6.hum1
    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
7h ago

Exploit prediction

0.41% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
GitHub 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm @modelcontextprotocol/sdk
<1.32.0
1.32.0
npm @modelcontextprotocol/client
>=2.0.0, <2.3.0
2.3.0

Affected products

  • modelcontextprotocol typescript-sdk
  • @modelcontextprotocol sdk
  • @modelcontextprotocol client

Classification

Weakness
  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor

References

Sources

Fencer Intel 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.