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CSV Injection in symfony/serializer

Moderate severity GitHub Reviewed Published Nov 24, 2021 in symfony/symfony • Updated Feb 5, 2024

Package

composer symfony/serializer (Composer)

Affected versions

>= 5.0.0, < 5.3.12
>= 4.1.0, < 4.4.35

Patched versions

5.3.12
4.4.35
composer symfony/symfony (Composer)
>= 4.1.0, < 4.4.35
>= 5.0.0, < 5.3.12
4.4.35
5.3.12

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

@fabpot fabpot published to symfony/symfony Nov 24, 2021
Published by the National Vulnerability Database Nov 24, 2021
Reviewed Nov 24, 2021
Published to the GitHub Advisory Database Nov 24, 2021
Last updated Feb 5, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS score

0.125%
(48th percentile)

Weaknesses

CVE ID

CVE-2021-41270

GHSA ID

GHSA-2xhg-w2g5-w95x

Source code

Credits

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