CVE-2021-41270: Prevent CSV Injection via formulas
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
@ by a tab
Since then, OWASP added 2 chars in that list: - Tab (0x09) - Carriage return (0x0D)
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
\r as well as
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.
Have found a security issue in Symfony? Send the details to security [at] symfony.com and don't disclose it publicly until we can provide a fix for it.
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