SB20261111159 - Authorization bypass through user-controlled key in mcp-gateway

Description

This security bulletin contains information about 1 vulnerability.

1) Authorization bypass through user-controlled key (CVE-ID: CVE-2026-109492)

CWE-ID: CWE-639 - Authorization Bypass Through User-Controlled Key

CVSSv4: 5.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N]

The vulnerability allows a remote user to access another user's resources, disclose workload logs, or disrupt that user's workloads.

The vulnerability exists due to authorization bypass through a user-controlled key in Microsoft MCP Gateway when handling network requests for user resources. A remote user can send specially crafted requests to read another user's workload logs or disrupt that user's workloads.

Remediation

Install update from vendor's website.

References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-109492
• https://ghcr.io/microsoft/mcp-gateway:1.0.0