PT-2026-137683

CVE-2026-123272

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Published

2026-11-05

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Updated

2026-11-05

Description by

CVSS 3.1
8.0
High
MetricsAV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
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.
Exploitability
Fix
Impacts
Researchers
Vendors
Affected products
Weakness enumeration
CWE-346: Origin Validation Error
Related identifiers
CVE-2026-123272
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