CVE-2021-41270mediumCWE-1236

CVE-2021-41270: medium-severity vulnerability in symfony

CSV Injection in Symfony

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 6.5epss 1.4%
In short

Symfony's CSV encoder could be tricked into creating malicious spreadsheet files that execute formulas when opened in Excel or similar applications. This happens because special characters weren't properly escaped, allowing attackers to inject code that runs automatically.

Technical detail

CSV injection vulnerability in Symfony's CsvEncoder affects versions 4.1.0-4.4.34 and 5.0.0-5.3.11. The encoder's `csv_escape_formulas` option failed to properly prefix cells starting with tab (0x09), carriage return (0x0D), =, +, -, or @ characters per OWASP guidelines, enabling formula injection when deserialized CSV data is exported and opened in spreadsheet applications. Fixed in versions 4.4.35 and 5.3.12 by adopting single quote prefixing for all dangerous characters.

Summary generated and translated by AI from the official description.
Symfony/Serializer handles serializing and deserializing data structures for Symfony, a PHP framework for web and console applications and a set of reusable PHP components. Symfony versions 4.1.0 before 4.4.35 and versions 5.0.0 before 5.3.12 are vulnerable to CSV injection, also known as formula injection. In Symfony 4.1, maintainers added the opt-in `csv_escape_formulas` option in the `CsvEncoder`, to prefix all cells starting with `=`, `+`, `-` or `@` with a tab `\t`. Since then, OWASP added 2 chars in that list: Tab (0x09) and Carriage return (0x0D). This makes the previous prefix char (Tab `\t`) part of the vulnerable characters, and OWASP suggests using the single quote `'` for prefixing the value. Starting with versions 4.4.34 and 5.3.12, Symfony now follows the OWASP recommendations and uses the single quote `'` to prefix formulas and add the prefix to cells starting by `\t`, `\r` as well as `=`, `+`, `-` and `@`.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Affected products
symfony · symfony
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