CVE-2021-41270Network attack vector

CSV formula injection via unsafe cell prefixing

Published Nov 24, 2021 · Updated Aug 4, 2024

CSV injection in Symfony Serializer 4.1.0 through 4.4.34 and 5.0.0 through 5.3.11 allows remote authenticated users to cause spreadsheet formula execution via crafted cell values. CsvEncoder's opt-in csv_escape_formulas option prefixes formula-leading cells with a tab, but tab and carriage-return prefixes remain recognized as formulas and the escaping omits those characters. Exploitation requires a Symfony application to export attacker-influenced data to CSV and a spreadsheet program to open the resulting file, enabling indirect data disclosure or other spreadsheet-side actions.

CVSS severity6.5
Medium
EPSS probability1.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSV injection in Symfony Serializer 4.1.0 through 4.4.34 and 5.0.0 through 5.3.11 allows remote authenticated users to cause spreadsheet formula execution via crafted cell values. CsvEncoder's opt-in csv_escape_formulas option prefixes formula-leading cells with a tab, but tab and carriage-return prefixes remain recognized as formulas and the escaping omits those characters. Exploitation requires a Symfony application to export attacker-influenced data to CSV and a spreadsheet program to open the resulting file, enabling indirect data disclosure or other spreadsheet-side actions.

The record

CVE
CVE-2021-41270
Published
Nov 24, 2021
Updated
Aug 4, 2024
Vendor
Symfony
Product
Symfony
Classifications
CWE-1236, T1204.002
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.1.0, < 4.4.35
  2. Affected versionversion=>= 5.0.0, < 5.3.12

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Symfony · Symfonyversion=>= 4.1.0, < 4.4.35; version=>= 5.0.0, < 5.3.12

Published CVSS scores

6.5GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1236Improper Neutralization of Formula Elements in a CSV File
T1204.002User Execution: Malicious File

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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