Medium severity · published Oct 27, 2026
CVE-2026-116684
Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource server
New
6.8
CVSS
0.4%
EPSS
No
On KEV
Description
The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.10.0 until 1.30.0 and 2.2.0, server-side bearer authentication configured through AuthSettings with token_verifier accepts a valid token issued for another service when the authorization server serves multiple resources and the TokenVerifier does not independently validate the aud audience. This resource-confusion flaw lets a token holder authenticate to the wrong MCP server and exercise that token's resulting access. This issue is fixed in versions 1.30.0 and 2.2.0.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 30% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PY
python-sdk · modelcontextprotocol
>= 1.10.0, < 1.30.0; >= 2.0.0, < 2.2.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-116684
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-116684
github.com
https://github.com/modelcontextprotocol/python-sdk/commit/0c9136841ff092987a20700ff9c2c9789bda2f40
github.com
https://github.com/modelcontextprotocol/python-sdk/commit/8c2fa6eabacde869d75568e33b9d466b58c2f512
github.com
https://github.com/modelcontextprotocol/python-sdk/pull/3447
github.com
https://github.com/modelcontextprotocol/python-sdk/pull/3451
github.com
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0
github.com
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0
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