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: - 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 \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.
{ "nvd_published_at": "2021-11-24T19:15:00Z", "cwe_ids": [ "CWE-1236" ], "severity": "MODERATE", "github_reviewed": true, "github_reviewed_at": "2021-11-24T20:04:02Z" }