CVE-2026-123271

Description

ChatCLI before v1.215.2 contains an improper validation vulnerability in the MCP OAuth login flow that uses server-supplied Protected Resource Metadata as the resource indicator without checking it matches the configured server URL. A malicious MCP server can declare another resource on the same authorization server, obtain the user's bearer token for it, and replay that token against the other resource.

References

• https://github.com/diillson/chatcli/blob/359eb27debc4de78289a9662551a51ab4528e16c/cli/mcp/oauth.go#L477-L493
• https://github.com/diillson/chatcli/commit/951fe24b8e090eae86bf8edb13a788916b1e6c91
• https://github.com/diillson/chatcli/releases/tag/v1.215.2
• https://github.com/diillson/chatcli/security/advisories/GHSA-95vg-3r9c-2v5q
• https://www.vulncheck.com/advisories/chatcli-before-1.215.2-origin-validation-error-via-unvalidated-mcp-oauth-resource-indicator