Security Bulletin
Summary
The terraform-mcp-server before version 1.1.0 is vulnerable to a cross-tenant credential reuse issue in the streamable-HTTP stateless transport mode that may allow one user's Terraform token to be used to execute tool calls on behalf of subsequent users. This vulnerability, CVE-2026-16498, is fixed in terraform-mcp-server 1.1.0.
Vulnerability Details
CVEID: CVE-2026-16498
DESCRIPTION: In stateless HTTP mode, the underlying MCP library does not assign unique session identifiers to requests. Because the server's per-session Terraform client cache relied on session identifiers to distinguish between users, it could not correctly isolate credentials across requests in this mode. This caused the credentials supplied by one tenant to be reused for subsequent requests from other tenants, regardless of the credentials those tenants supplied. The issue affects only deployments explicitly configured to use stateless HTTP mode; deployments using the default stateful HTTP mode or stdio mode are not affected.
CWE: CWE-488: Exposure of Data Element to Wrong Session
CVSS Source: HashiCorp Inc.
CVSS Base score: 10
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| terraform-mcp-server | affected from 0.3.0 up to 1.1.0 |
Remediation/Fixes
Customers should evaluate the risk associated with this issue and consider upgrading to terraform-mcp-server 1.1.0. Operators running stateless HTTP mode deployments who cannot upgrade immediately should disable stateless mode by removing the MCP_SESSION_MODE=stateless configuration and restarting in the default stateful mode, or by restricting the server to a single trusted tenant until the upgrade can be applied.
Get Notified about Future Security Bulletins
References
Link to HashiCorp Security Bulletin: https://discuss.hashicorp.com/t/hcsec-2026-23-multiple-vulnerabilities-impacting-hashicorp-terraform-mcp-server/77606
Acknowledgement
This issue was identified by an internal team.
Change History
28 Jul 2026: Initial Publication
*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.
Disclaimer
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Document Location
Worldwide
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Document Information
Modified date:
28 July 2026
Initial Publish date:
28 July 2026
UID
ibm17281662