Vulnerability in Diillson Chatcli
CVE-2026-123271
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/diillson/chatcli/blob/359eb27debc4de78289a9662551a51ab4528e16c/cli/m… (technical-description)
- github.com/diillson/chatcli/commit/951fe24b8e090eae86bf8edb13a788916b1e6c91 (patch)
- ChatCLI v1.215.2 Release Notes (release-notes)
- GitHub Security Advisory (GHSA-95vg-3r9c-2v5q) (vendor-advisory)
- VulnCheck Advisory: ChatCLI before v1.215.2 Origin Validation Error via Unvalidated MCP OAuth Resource Indicator (third-party-advisory)
Frequently asked questions
- What is CVE-2026-123271?
- CVE-2026-123271 is a high-severity vulnerability in Diillson Chatcli, classified under Origin Validation Error. CVSS score: 8.0/10. Published 2026-11-05.
- How severe is CVE-2026-123271?
- High severity. CVSS v3 base score is 8.0 out of 10.