CVE-2026-104850 MCP TypeScript SDK - Authentication Bypass

MCP TypeScript SDK <= 1.12.0 and < 1.31.0, 2.x < 2.2.0 contains an OAuth client authorization bypass caused by unbound stored credentials to authorization servers, letting malicious MCP servers receive client OAuth credentials without user interaction, exploit requires untrusted MCP server connection.

CVSS base score 7.5 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.18% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Information Disclosure
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Published
6 October 2026
Updated
15 October 2026
Weakness
CWE-345

Vendor fix

Upgrade to @modelcontextprotocol/sdk 1.31.0 or @modelcontextprotocol/client 2.2.0 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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