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Fencer Vulns
high 8.0

CVE-2026-123271 json

ChatCLI before v1.215.2 Origin Validation Error via Unvalidated MCP OAuth Resource Indicator

published 2026-11-05 3 d ago modified 2026-11-08 26 h ago also EUVD-2026-117724

cvss
8.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

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.

Patch / fix

  • diillson ChatCLI v1.215.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-123271 updated cvss 8.0

github.com/diillson/chatcli: ChatCLI: Unauthorized access via unvalidated MCP OAuth resource indicator

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 5.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
CNA 3.1 8.0 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
CNA 4.0 5.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • diillson ChatCLI

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.