| Package | Affected versions | Patched versions |
|---|---|---|
| symfony/serializer | ≥ 4.1.0, < 4.4.35≥ 5.0.0, < 5.3.12 | 4.4.355.3.12 |
| symfony/symfony | ≥ 4.1.0, < 4.4.35≥ 5.0.0, < 5.3.12 | 4.4.355.3.12 |
| symfony | ≥ 4.1.0, < 4.4.35≥ 5.0.0, < 5.3.12 | 4.4.355.3.12 |
CSV Injection, also known as Formula Injection, occurs when websites embed untrusted input inside CSV files. When a spreadsheet program opens a CSV, any cell starting with = is interpreted by the software as a formula and could be abused by an attacker.
In Symfony 4.1, we've added the opt-in csv_escape_formulas option in CsvEncoder, to prefix all cells starting by =, +, - or @ by a tab \t.
Since then, OWASP added 2 chars in that list:
This makes our previous prefix char (Tab \t) part of the vulnerable characters, and OWASP suggests using the single quote ' for prefixing the value.
Symfony now follows the OWASP recommendations and use the single quote ' to prefix formulas and adds the prefix to cells starting by \t, \r as well as =, +, - and @.
The patch for this issue is available here for branch 4.4.
We would like to thank Jake Barwell for reporting the issue and Jérémy Derussé for fixing the issue.
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