CVE-2026-76797 in BI Connector Transition Readiness Report
Summary
by MITRE • 08/28/2026
The MongoSQL Transition Readiness Tool writes database and collection names into its generated CSV reports without neutralizing leading characters that spreadsheet applications treat as formulas. A user with write privileges on the cluster can choose a namespace name that is later evaluated as a formula when an operator opens the generated report in a spreadsheet application, which may result in unintended disclosure of report contents or execution of external content on the operator's workstation. Generating a report for the affected namespace and opening it in a spreadsheet application is required.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified involves a classic injection flaw within the MongoSQL Transition Readiness Tool, specifically categorized under CWE-798: Use of Hard-coded Credentials or CWE-20: Improper Input Validation depending on the specific vector, but most accurately aligned with CWE-116: Improper Encoding or Escaping of Output. The core technical flaw lies in the tool's failure to sanitize namespace names when generating CSV reports. Spreadsheet applications such as Microsoft Excel and LibreOffice Calc interpret certain characters at the beginning of a cell value as formula indicators. By writing database and collection names directly into these fields without escaping leading equals signs, plus signs, minus signs, or tab characters, the application allows an attacker-controlled string to be executed as code when the file is opened. This behavior transforms standard data storage into a potential execution vector for malicious commands embedded within what appears to be benign metadata.
From an operational perspective, this vulnerability poses significant risks related to both confidentiality and integrity of user environments. A threat actor with write privileges on the MongoDB cluster can craft specific namespace names that contain formula syntax. When another operator generates a report using these namespaces and subsequently opens the resulting CSV file in a spreadsheet application, the software automatically evaluates the embedded string as a command rather than displaying it as text. This mechanism facilitates unintended disclosure of sensitive information contained within other cells or rows due to side effects of certain formulas, such as those that read cell ranges. Furthermore, more sophisticated payloads can trigger requests to external servers, leading to remote code execution on the operator's workstation if combined with macro-enabled formats or specific application vulnerabilities. The attack requires social engineering elements where the victim must actively generate and open the report, placing it within the context of ATT&CK technique T1566.002: Spearphishing Link, although adapted for internal tool misuse rather than external phishing emails.
The impact extends beyond simple data leakage to include potential compromise of the analyst's machine through drive-by downloads or credential harvesting if the formula interacts with network resources. For instance, a payload utilizing HYPERLINK functions can direct users to malicious sites upon opening, while other formulas might exfiltrate local file paths or system information back to an attacker-controlled server via HTTP requests initiated by the spreadsheet engine. This represents a severe risk in environments where security teams rely on automated reporting tools for compliance and readiness assessments, as it undermines trust in internal tooling and exposes personnel to secondary attacks originating from trusted sources within their own infrastructure.
Mitigation strategies must focus on input validation at both the application level and user awareness levels. The primary technical fix involves implementing strict output encoding or escaping mechanisms within the MongoSQL Transition Readiness Tool to ensure that any special characters, particularly leading equals signs, are treated as literal text rather than executable syntax. This can be achieved by prefixing problematic values with a single quote character, which forces spreadsheet applications to interpret the content as plain text. Additionally, input validation should reject or sanitize namespace names containing formula-indicating prefixes before they are written to any output files. Organizations should also enforce policies that discourage opening CSV reports from untrusted sources and configure default security settings in spreadsheet software to disable automatic macro execution and external content evaluation by default. Regular audits of internal tools for similar injection vulnerabilities across different data export formats are recommended to prevent recurrence of this class of issues.