Uni-CLI: Browser-to-localhost access via legacy HTTP MCP transport
Summary
Uni-CLI before 0.225.2 accepted requests from browser origins on the legacy JSON-RPC-over-HTTP MCP transport without checking the Origin header. A malicious web page visited by a user can send a simple cross-origin POST to the local /mcp endpoint and call Uni-CLI tools, but only if the user has started the legacy HTTP MCP transport. The vendor states that the issue does not change Uni-CLI's local code-execution trust model, and the impact depends on which local tools are exposed to agents.
Affected
- Uni-CLI (npm package @zenalexa/unicli) versions before 0.225.2
- Only installations that run the legacy HTTP MCP transport are exposed.
- The lower bound of the affected range is not confirmed. A third-party analysis suggests 0.208.0.
Fixed in
- Version 0.225.2 (released 15 Jun 2026)
Workaround
- Upgrade to 0.225.2 or later.
- If an upgrade is not immediately possible, do not use the legacy HTTP MCP transport for browser-originated traffic. Use the default stdio transport or the Streamable HTTP transport instead.
Exploitation
- No known exploitation in the wild.
- No public proof of concept found.
- CISA SSVC: exploitation none, automatable yes, technical impact total.
- EPSS is very low (about 0.0027).
Our recommendation
- Check whether @zenalexa/unicli is installed on workstations and which version is used (for example with npm ls -g).
- Upgrade to 0.225.2 or later, including copies embedded in other tools.
- Where patching is not immediately possible, turn off the legacy HTTP MCP transport and use stdio.
- Keep browsers on managed workstations up to date and monitor the GitHub advisory for updates.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Uni-CLI release v0.225.2 github.com
- GitHub Security Advisory GHSA-v3f4-w7r7-v3hm github.com
- GitHub Advisory GHSA-v3f4-w7r7-v3hm (advisories) github.com
- OSV GHSA-v3f4-w7r7-v3hm osv.dev
- VulDB 425977 vuldb.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 07:10.
Original description (NVD)
Uni-CLI gives people and agents one command interface for websites, browsers, desktop applications, local tools, and MCP. Prior to version 0.225.2, Uni-CLI exposed the legacy JSON-RPC-over-HTTP MCP transport on loopback without validating browser Origin headers before routing requests. A malicious web page could send a CORS simple POST request, such as text/plain, to the local /mcp endpoint and deliver a JSON-RPC body to the dispatcher. If the user had started the local MCP HTTP transport, that page could drive tools/call requests against the user's local Uni-CLI server. The Streamable HTTP transport already enforced this browser-to-localhost boundary. The legacy stateless HTTP path did not, so the two HTTP transports had drifted. This issue is about the browser-to-localhost boundary; it does not change Uni-CLI's local-code-execution trust model. This issue has been patched in version 0.225.2.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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