CVE-2026-33032: nginx-ui's Unauthenticated MCP Endpoint Allows Remote Nginx Takeover

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 2.5%, percentile 85: FIRST’s model estimates a 2.5% chance of exploitation activity in the next 30 days, higher than 85% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes github.com/0xJacky/Nginx-UI (Go) <= 1.99, no fixed version listed. Check your lockfile, including transitive dependencies.

What it is

Nginx UI is a web user interface for the Nginx web server. In versions 2.3.5 and prior, the nginx-ui MCP (Model Context Protocol) integration exposes two HTTP endpoints: /mcp and /mcpmessage. While /mcp requires both IP whitelisting and authentication (AuthRequired() middleware), the /mcpmessage endpoint only applies IP whitelisting - and the default IP whitelist is empty, which the middleware treats as "allow all". This means any network attacker can invoke all MCP tools without authentication, including restarting nginx, creating/modifying/deleting nginx configuration files, and triggering automatic config reloads - achieving complete nginx service takeover. At time of publication, there are no publicly available patches.

From the GitHub advisory

Summary The nginx-ui MCP (Model Context Protocol) integration exposes two HTTP endpoints: /mcp and /mcpmessage. While /mcp requires both IP whitelisting and authentication (AuthRequired() middleware), the /mcpmessage endpoint only applies IP whitelisting - and the default IP whitelist is empty, which the middleware treats as "allow all". This means any network attacker can invoke all MCP tools without authentication, including restarting nginx, creating/modifying/deleting nginx configuration files, and triggering automatic config reloads - achieving complete nginx service takeover.

Details Vulnerable Code

mcp/router.go:9-17 - Auth asymmetry between endpoints

The /mcp endpoint has middleware.AuthRequired(), but /mcpmessage does not. Both endpoints route to the same mcp.ServeHTTP() handler, which processes all MCP tool invocations.

internal/middleware/ipwhitelist.go:11-26 - Empty whitelist allows all

Weakness type: CWE-306.

Product: github.com/0xJacky/Nginx-UI (Go) · Assigned by: GitHub_M · Published: 2026-03-30

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 2.52% probability of exploitation activity in the next 30 days; percentile 85.

Timeline

• 2026-03-30 — CVE record published by GitHub_M
• 2026-03-30 — GitHub-reviewed advisory GHSA-h6c2-x2m2-mwhf published (critical)
• 2026-04-16 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-h6c2-x2m2-mwhf github.com
2. CVE.org record CVE-2026-33032 cve.org
3. NVD entry CVE-2026-33032 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. websec.net websec.net
3. github.com github.com
4. github.com github.com

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