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GHSA-2xhg-w2g5-w95xmedium6.5

CSV Injection in symfony/serializer

Impact

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.

Source excerpt · OSV

Affected packages

Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.

symfony/serializer Packagist
Affected rangeRecorded fix
From 5.0.0 before 5.3.12Ecosystem versions5.3.12
From 4.1.0 before 4.4.35Ecosystem versions4.4.35

Version evidence: OSV · GHSA-2xhg-w2g5-w95x

View original version evidence (128 explicit versions)
symfony/symfony Packagist
Affected rangeRecorded fix
From 4.1.0 before 4.4.35Ecosystem versions4.4.35
From 5.0.0 before 5.3.12Ecosystem versions5.3.12

Version evidence: OSV · GHSA-2xhg-w2g5-w95x

View original version evidence (147 explicit versions)

Original source description

Description

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.

Resolution

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.

Credits

We would like to thank Jake Barwell for reporting the issue and Jérémy Derussé for fixing the issue.

References