Description

Improper Encoding or Escaping of Output vulnerability in Apache Syncope. Authenticated users can store a spreadsheet formula payload in one of their own plain attributes. When such users are included in a CSV export and the generated CSV file is opened by a spreadsheet application, the formula may be executed. This issue affects Apache Syncope: from 3.0.0-M0 through 3.0.16, from 4.0.0-M0 Through 4.0.7, from 4.1.0-M0 through 4.1.2. Users are recommended to upgrade to version 4.0.8 / 4.1.3, which fix this issue.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.3",
  "pubDate": "2026-09-14T14:17:08.597Z",
  "pubdate": "2026-09-14T14:17:08.597Z",
  "executiveSummary": "This vulnerability is classified as Improper Encoding or Escaping of Output, specifically manifesting as a CSV Injection (Formula Injection) flaw within Apache Syncope.\nThe issue allows authenticated users to inject malicious spreadsheet formulas into plain attributes, which are subsequently rendered by spreadsheet software when exporting data to CSV format.\nSuccessful exploitation could lead to unauthorized code execution, data exfiltration, or local system interaction if a privileged user or administrator opens the maliciously crafted CSV file in a vulnerable spreadsheet application.\nAffected products include 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.\nThe vulnerability requires the attacker to have authenticated access to the system to modify their own user attributes.\nRisk mitigation centers on upgrading to the patched versions (4.0.8 / 4.1.3) and implementing rigorous input sanitization strategies.",
  "technicalDetails": "The root cause of this vulnerability lies in the improper sanitization and encoding of user-supplied input when generating CSV reports. Apache Syncope fails to intercept or neutralize characters that hold special significance to spreadsheet processors (such as =, +, -, or @) when they appear at the beginning of a cell value.\nWhen an authenticated user updates a plain attribute within their profile, they can inject a formula-based payload. Because the application does not validate or sanitize these attributes prior to including them in the CSV export stream, the resulting CSV file contains the raw, malicious string.\nThe attack flow proceeds as follows: 1. The attacker authenticates to the Apache Syncope instance. 2. The attacker modifies a plain attribute with a crafted spreadsheet formula payload (e.g., '=cmd|'/C calc'!A0'). 3. An administrator or another user triggers a CSV export of user data from the management console. 4. The Apache Syncope backend generates a CSV file, embedding the malicious payload directly into the output file without prefixing it with an escape character (such as a single quote). 5. The target opens the CSV file using a spreadsheet application like Microsoft Excel or LibreOffice Calc. 6. The spreadsheet application interprets the injected string as an executable formula, triggering the payload execution.\nThe impact is determined by the capabilities of the spreadsheet application used by the victim. If the application is configured to execute macros or external commands, the injected payload may result in remote code execution (RCE) on the victim's machine. Even without RCE, attackers can use formulas to exfiltrate data from other cells or pivot to internal network resources by referencing external URLs.\nThis vulnerability is present in 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. The lack of output encoding for CSV cells specifically constitutes the security oversight.\nPost-exploitation impact ranges from local system compromise to the inadvertent disclosure of sensitive data through DDE (Dynamic Data Exchange) links or malicious formula execution within the spreadsheet environment."
}