CSV Injection in symfony/serializer
Summary
CVE-2021-41270: CSV Injection in symfony/serializer. Affects symfony/serializer across 2 version ranges.
>= 4.1.0, < 4.4.35
>= 5.0.0, < 5.3.12
Fixed in 4.4.35 or 5.3.12, depending on the release line you run. How to fix ↓
Also tracked for
The same CVE-2021-41270 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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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.
How To Fix
Fixed versions by release line
The minimum fixed version depends on the release line you run.
-
>= 4.1.0, < 4.4.354.4.35composer require symfony/serializer:4.4.35 -
>= 5.0.0, < 5.3.125.3.12composer require symfony/serializer:5.3.12
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References
Related vulnerabilities
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