ChatCLI before v1.215.2 Origin Validation Error via Unvalidated MCP OAuth Resource Indicator
- Exploited
- No known exploitation
- Fix
- Fixed in v1.215.2
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: v1.215.2.
- Published
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 12/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
A malicious MCP server can trick ChatCLI, in versions before v1.215.2, into sending the user's OAuth bearer token to a different resource on the same authorization server, and then replay that token against it. The attack is network-based and needs no login, but it does require the user to take an action, and the flaw's main effect is exposing that token to another resource.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original 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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure7/25Reachable over the network without a login · Unknown: No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity5.1/10CVSS 5.1
- No patch0/5No signal
What would change the score
- Would score about 67 if added to CISA KEV
- Would score about 62 if CISA's SSVC rates exploitation active
- Would score about 27 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: v1.215.2.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- diillson ChatCLI
From v1.159.0 · fixed in v1.215.2
Evidence 5
- Advisory
- Patch
- Repository
- Repository
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-123271
Is CVE-2026-123271 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-123271?
ChatCLI: from v1.159.0 before v1.215.2.Source: cve.now feed data
How do I fix CVE-2026-123271?
Upgrade to a fixed version: v1.215.2.Source: cve.now feed data