Skip to content
Patch Next
Sign inAdd to your agent

← Actionable
Medium, CVSS 6.5

CSV Injection in symfony/serializer

CVE-2021-41270GHSA-2xhg-w2g5-w95x

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (symfony/symfony 5.3.12, 4.4.35; symfony/serializer 5.3.12, 4.4.35), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

Add to your agent

Affected packages

  • Packagist symfony/symfony

    Affected
    >= 4.1.0, < 4.4.35>= 5.0.0, < 5.3.12
    Fixed in
    5.3.12, 4.4.35

  • Packagist symfony/serializer

    Affected
    >= 5.0.0, < 5.3.12>= 4.1.0, < 4.4.35
    Fixed in
    5.3.12, 4.4.35

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
6.5 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
EPSS
  • CVE-2021-41270: 1.40% estimated exploitation activity in the next 30 days; percentile 72.53 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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 csvescapeformulas 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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-2xhg-w2g5-w95x

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2021-41270

Advisory: CSV Injection in symfony/serializer
IDs: CVE-2021-41270, GHSA-2xhg-w2g5-w95x
Record: https://patchnext.com/advisories/cve-2021-41270 (revision 1, source checked 26 Oct 2026, 14:15 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: symfony/symfony 5.3.12, 4.4.35; symfony/serializer 5.3.12, 4.4.35. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist symfony/symfony: affected >= 4.1.0, < 4.4.35; >= 5.0.0, < 5.3.12; fixed in 5.3.12, 4.4.35
- Packagist symfony/serializer: affected >= 5.0.0, < 5.3.12; >= 4.1.0, < 4.4.35; fixed in 5.3.12, 4.4.35

## Suggested inspection (read-only)
- Packagist symfony/symfony: check the installed version with your package manager.
- Packagist symfony/serializer: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on symfony/symfony, symfony/serializer.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2xhg-w2g5-w95x (GitHub-reviewed advisory GHSA-2xhg-w2g5-w95x lists affected ranges: Packagist symfony/serializer >=5.0.0 =4.1.0 =4.1.0 =5.0.0 <5.3.12)

Commands are suggestions: review each one before running it.

Loading voting…