CVE-2026-76794: MongoSQL Transition Tool XSS Vulnerability

CVE-2026-76794 Overview

CVE-2026-76794 is a stored cross-site scripting (XSS) vulnerability in the MongoSQL Transition Readiness Tool. The tool does not sufficiently encode database metadata before embedding it into generated HTML reports. A MongoDB user with write access can inject crafted metadata that executes script code when another user generates and opens the report. Successful exploitation can expose report contents or alter the report display in the victim's browser. The weakness is classified under CWE-79: Improper Neutralization of Input During Web Page Generation.

Critical Impact
An authenticated MongoDB user with write privileges can plant JavaScript payloads in database metadata that execute in the browser context of any user who generates and opens a transition readiness report.

Affected Products

MongoSQL Transition Readiness Tool
MongoDB SQL Interface tooling that ingests database metadata for HTML report generation
Downstream reports produced by the tool for MongoSQL migration assessments

Discovery Timeline

2026-08-28 - CVE-2026-76794 published to the National Vulnerability Database (NVD)
2026-08-31 - Last updated in the NVD database

Technical Details for CVE-2026-76794

Vulnerability Analysis

The MongoSQL Transition Readiness Tool scans a MongoDB deployment and generates an HTML report describing schema, collection, and field metadata. During report generation, the tool inserts database metadata values directly into the HTML output without applying context-appropriate output encoding. Because the metadata originates from a data store that any user with write access can modify, adversarial values become active script when rendered by a browser.

This is a stored XSS pattern. The payload is persisted in MongoDB and delivered later, when a privileged operator generates the report and opens it locally or in a shared location. The victim's browser executes the injected script in the origin used to view the report, which may include local file context or an internal host. The vulnerability requires user interaction, since another user must generate and open the report for the payload to fire.

Root Cause

The root cause is missing HTML entity encoding on untrusted input. Metadata fields such as collection names, field names, or descriptive attributes are concatenated into the report template rather than escaped. Characters including <, >, ", ', and & retain their HTML meaning, allowing an attacker to close attributes or open a new <script> element inside the report DOM.

Attack Vector

An attacker first obtains write access to a MongoDB instance that will later be scanned. The attacker stores crafted metadata, for example a collection or field name containing a <script> payload or an event-handler attribute. When an administrator runs the MongoSQL Transition Readiness Tool against that instance and opens the resulting HTML report, the browser parses and executes the attacker's script. The script can read report contents, exfiltrate them, or manipulate what the reviewer sees. No network-facing service exposure beyond MongoDB write access is required, and no elevated privileges on the report generator are needed prior to execution.

No verified public proof-of-concept code is available. See the MongoDB SQL Interface Changelog for vendor technical details.

Detection Methods for CVE-2026-76794

Indicators of Compromise

MongoDB collection, field, or index names containing HTML control characters such as <, >, or ", or containing substrings like <script, onerror=, or javascript:.
Transition readiness HTML reports that render unexpected UI elements, blank sections, or trigger outbound network requests when opened.
Browser console errors or Content Security Policy violations when opening a MongoSQL readiness report.

Detection Strategies

Audit MongoDB metadata across databases and collections for names or descriptions that include HTML tags, quotes, or JavaScript URI schemes.
Statically scan generated report HTML for unexpected <script> tags, inline event handlers, or javascript: URIs prior to distribution.
Correlate MongoDB write activity from low-privilege accounts with subsequent report generation events to identify suspicious injection windows.

Monitoring Recommendations

Enable MongoDB auditing on schema and metadata write operations, and alert on identifiers containing HTML control characters.
Monitor endpoints where administrators open readiness reports for anomalous browser child processes or outbound connections initiated from local HTML files.
Track access to report output directories and shared locations to identify who has opened potentially poisoned reports.

How to Mitigate CVE-2026-76794

Immediate Actions Required

Upgrade the MongoSQL Transition Readiness Tool to the latest version referenced in the MongoDB SQL Interface Changelog.
Restrict MongoDB write access to trusted principals only, and review recent grants of write roles on databases scanned by the tool.
Inspect existing readiness reports for injected script content before sharing or reopening them.

Patch Information

MongoDB tracks fixes for the MongoSQL Transition Readiness Tool in the MongoDB SQL Interface Changelog. Apply the fixed release identified there. No additional vendor advisory URLs were published in the NVD record at the time of publication.

Workarounds

Sanitize MongoDB metadata before running the tool by renaming collections, fields, or attributes that contain HTML control characters.
Open generated reports only in a hardened browser profile with JavaScript disabled or under a strict Content Security Policy.
Generate reports in an isolated environment that has no access to sensitive credentials, cookies, or internal networks.

bash

# Identify MongoDB collections whose names contain HTML control characters
mongosh --quiet --eval '
  db.getMongo().getDBNames().forEach(function(name) {
    var d = db.getSiblingDB(name);
    d.getCollectionNames().forEach(function(c) {
      if (/[<>"'\''&]|script|onerror|javascript:/i.test(c)) {
        print(name + "." + c);
      }
    });
  });
'