---
id: "CVE-2026-123271"
kind: "vulnerability"
aliases: ["CVE-2026-123271"]
title: "ChatCLI: MCP OAuth login can leak bearer tokens to other resources"
severity: "high"
cvss: 8.0
epss: null
exploited: false
status: "open"
category: "ai-tooling"
products: []
ecosystems: []
tags: ["ai-tooling", "chatcli", "developers", "mcp", "oauth"]
not_affected_if: ["no-mcp-oauth", "no-untrusted-mcp-servers"]
published_at: "2026-11-05T19:17:20+00:00"
first_seen_at: "2026-11-05T19:40:36+00:00"
updated_at: "2026-11-05T19:42:56+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123271", "first_seen_at": "2026-11-05T19:40:36+00:00"}]
exploit_sources: []
---

# ChatCLI: MCP OAuth login can leak bearer tokens to other resources

ChatCLI before v1.215.2 trusts the resource URL that a remote MCP server supplies during its OAuth login flow without checking it against the configured server. A malicious MCP server can get a user's bearer token issued for another resource and then replay that token against it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed ChatCLI version and confirm whether it is below `v1.215.2`.
- Look for MCP servers configured in ChatCLI that use OAuth login.

## Fix

- ChatCLI: move to `v1.215.2` or later.

## Timeline

- 2026-11-05T19:40:36+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123271

## Documents

- [advisory] Vendor advisory: github.com https://github.com/diillson/chatcli/security/advisories/GHSA-95vg-3r9c-2v5q
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/chatcli-before-1.215.2-origin-validation-error-via-unvalidated-mcp-oauth-resource-indicator
- [fix] Patch: github.com https://github.com/diillson/chatcli/commit/951fe24b8e090eae86bf8edb13a788916b1e6c91
- [fix] Release notes: github.com https://github.com/diillson/chatcli/releases/tag/v1.215.2

## From the sources

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.

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