CVE-2021-41270

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 `@`.

How to fix CVE-2021-41270

To remediate CVE-2021-41270, upgrade the affected package to a fixed version below.

• —upgrade to 4.4.35 or later
• —upgrade to 4.4.19+dfsg-2+deb11u1 or later
• —upgrade to 5.3.12 or later
• —upgrade to 4.4.35 or later

Is CVE-2021-41270 being exploited?

Low — EPSS is 0.9%, meaning exploitation activity has not been observed at scale.

Affected packages (4)

• >= 4.1.0, < 4.4.35, >= 5.0.0, < 5.3.12
• from 0, < 4.4.19+dfsg-2+deb11u1
• >= 5.0.0, < 5.3.12
• >= 4.1.0, < 4.4.35

CVSS scores

References (16)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2021-41270
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2021-41270
• PATCHgithub.com/symfony/symfony
• WEBgithub.com/FriendsOfPHP/security-advisories/blob/master/symfony/serializer/CVE-2021-41270.yaml