Vulnerability · Published Nov 5, 2026 · Assigned by VulnCheck

CVE-2026-123271ChatCLI before v1.215.2 Origin Validation Error via Unvalidated MCP OAuth Resource Indicator

High 8.0

In plain English

A high-severity security flaw in ChatCLI from diillson. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 4% of all known vulnerabilities).

Severity (CVSS 3.1)8.0High

Exploit odds (30 days)0.1%top 96.1% of all CVEs

Exploited in the wildNo reportsnot in CISA KEV

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
diillson	ChatCLI	v1.159.0 – before v1.215.2

Weakness: CWE-346 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N

References

GitHub Security Advisory (GHSA-95vg-3r9c-2v5q) vendor-advisory
https://github.com/diillson/chatcli/commit/951fe24b8e090eae86bf8edb13a788916b1e6c91 patch
ChatCLI v1.215.2 Release Notes release-notes
https://github.com/diillson/chatcli/blob/359eb27debc4de78289a9662551a51ab4528e16c/cli/mcp/oauth.go#L477-L493 technical-description
VulnCheck Advisory: ChatCLI before v1.215.2 Origin Validation Error via Unvalidated MCP OAuth Resource Indicator third-party-advisory