Vulnerability CVE-2021-41270


Published: 2021-11-24

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 `@`.

Type:

CWE-1236

CVSS2 => (AV:N/AC:L/Au:S/C:P/I:N/A:N)

CVSS Base Score
Impact Subscore
Exploitability Subscore
4/10
2.9/10
8/10
Exploit range
Attack complexity
Authentication
Remote
Low
Single time
Confidentiality impact
Integrity impact
Availability impact
Partial
None
None
Affected software
Sensiolabs -> Symfony 

 References:
https://github.com/symfony/symfony/commit/3da6f2d45e7536ccb2a26f52fbaf340917e208a8
https://github.com/symfony/symfony/security/advisories/GHSA-2xhg-w2g5-w95x
https://github.com/symfony/symfony/releases/tag/v5.3.12
https://github.com/symfony/symfony/pull/44243

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