CVE-2026-123272

HighCVSS 8.0/10Last modified Nov 8, 2026

Description

Mark3labs mcp-go before v1.2.1 contains an improper validation vulnerability in OAuthHandler.fetchServerMetadata that allows malicious MCP servers to obtain tokens for other resources by declaring arbitrary resources in well-known metadata. Attackers can declare a different MCP server as the RFC 8707 resource indicator, causing the authorization server to mint tokens the attacker replays against that resource.

Metrics

CVSS 3.1 8.0/10CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N

Weakness enumeration

CWE-346

Affected software

No affected versions have been published.

Timeline

Published
Nov 5, 2026
Last modified
Nov 8, 2026
NVD status
Deferred

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CVE-2026-123272: High severity, CVSS 8.0 | Vulnix