CVE-2026-76798 Overview
The MongoSQL Transition Readiness Tool contains a stored cross-site scripting (XSS) vulnerability [CWE-79]. The tool reads query text and user names from BI Connector log files and writes them into a generated HTML report without encoding the content for that output context. An authenticated user who can issue queries through the BI Connector can inject markup into log entries. When an operator later generates the report and opens it in a browser, the browser interprets the injected markup. This can disclose other users' logged query text and user names to an external party or present misleading content to the operator.
Critical Impact
A low-privileged BI Connector user can plant markup in query logs that executes in an operator's browser when the readiness report is opened, exposing logged queries and user names.
Affected Products
- MongoSQL Transition Readiness Tool
- MongoDB BI Connector (log source)
- HTML report output component of the readiness tool
Discovery Timeline
- 2026-08-28 - CVE-2026-76798 published to the National Vulnerability Database (NVD)
- 2026-08-31 - Last updated in NVD database
Technical Details for CVE-2026-76798
Vulnerability Analysis
The MongoSQL Transition Readiness Tool generates an HTML report summarizing queries observed in BI Connector logs. During report generation, the tool ingests query strings and user names from log files and inserts them into the HTML document as-is. Because these values pass through without HTML entity encoding, any characters with markup meaning (<, >, ", ') are rendered as active HTML instead of literal text.
Exploitation follows a stored XSS pattern. The attacker acts as a BI Connector user with permission to submit SQL queries. The attacker crafts a query whose text contains HTML or JavaScript, for example a <script> tag or an event-handler attribute. The BI Connector logs that query, and the readiness tool later embeds it in the report. When an operator opens the report locally in a browser, the injected payload executes in the file or origin context of the report page.
The impact is bounded by the operator's browsing context. The payload can read report content, exfiltrate logged query text and user names to an attacker-controlled endpoint, or render deceptive UI to mislead the operator reviewing the readiness output.
Root Cause
The report writer does not apply context-appropriate output encoding. Log-derived strings are placed into HTML element and attribute contexts without escaping metacharacters, violating the standard defense against stored XSS described in CWE-79.
Attack Vector
The attack requires network access to the BI Connector, valid low-privileged credentials to issue queries, and later user interaction from an operator who generates the report and opens it in a browser. See the MongoDB SQL Interface Changelog for the fixed release notes.
The vulnerability is described in prose only; no verified proof-of-concept code has been published. The exploitation pattern involves supplying HTML markup as part of a SQL query string so that it is captured verbatim in the BI Connector log, then rendered unescaped by the report generator.
Detection Methods for CVE-2026-76798
Indicators of Compromise
- BI Connector log entries containing HTML tags, <script> markup, or JavaScript event handlers (onerror=, onload=) embedded in query text or user name fields.
- Generated readiness report HTML files that include outbound requests to unfamiliar domains when opened.
- Operator browser sessions issuing unexpected network requests immediately after opening a readiness report.
Detection Strategies
- Scan BI Connector query logs for markup metacharacters and script keywords before generating a readiness report.
- Inspect generated HTML reports for <script>, <iframe>, or attribute-based handlers within query or user name fields.
- Correlate query submissions containing markup payloads with the submitting user account to identify the source.
Monitoring Recommendations
- Forward BI Connector logs to a centralized logging platform and alert on markup patterns in query text.
- Monitor operator workstations for outbound connections initiated by browsers viewing local report files.
- Track which accounts have permission to submit queries through the BI Connector and review that list against operational need.
How to Mitigate CVE-2026-76798
Immediate Actions Required
- Upgrade the MongoSQL Transition Readiness Tool to a fixed release listed in the MongoDB SQL Interface Changelog.
- Do not open readiness reports generated from untrusted or unreviewed log data in a production browser profile.
- Restrict BI Connector query permissions to trusted users while a patched version is being deployed.
Patch Information
MongoDB has addressed the encoding defect in the readiness tool. Consult the vendor changelog referenced above for the specific fixed version and apply it before generating new reports over historical logs.
Workarounds
- Generate readiness reports only over log files whose contents have been reviewed for markup metacharacters.
- Open generated reports in an isolated browser profile or sandboxed environment with no access to sensitive origins.
- Preprocess BI Connector log files to strip or HTML-encode <, >, ", and ' in query text and user name fields prior to report generation.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
