What’s Vulnerable › Vulnerabilities

CVE-2020-26256: Denial of service in fast-csv

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-12-08 · updated 2026-06-17
• Weakness: CWE-400

Description

Fast-csv is an npm package for parsing and formatting CSVs or any other delimited value file in node. In fast-cvs before version 4.3.6 there is a possible ReDoS vulnerability (Regular Expression Denial of Service) when using ignoreEmpty option when parsing. This has been patched in `v4.3.6` You will only be affected by this if you use the `ignoreEmpty` parsing option. If you do use this option it is recommended that you upgrade to the latest version `v4.3.6` This vulnerability was found using a CodeQL query which identified `EMPTY_ROW_REGEXP` regular expression as vulnerable.

Affected products

• C2FO fast-csv: before 4.3.6 — fixed in 4.3.6

How to fix

Upgrade to a fixed version: C2FO fast-csv 4.3.6. Check the vendor advisory for mitigations.

References

• https://github.com/C2FO/fast-csv/commit/4bbd39f26a8cd7382151ab4f5fb102234b2f829e
• https://github.com/C2FO/fast-csv/issues/540
• https://github.com/C2FO/fast-csv/security/advisories/GHSA-8cv5-p934-3hwp
• https://lgtm.com/query/8609731774537641779/
• https://www.npmjs.com/package/%40fast-csv/parse
• https://www.npmjs.com/package/fast-csv
• https://github.com/C2FO/fast-csv/commit/4bbd39f26a8cd7382151ab4f5fb102234b2f829e
• https://github.com/C2FO/fast-csv/issues/540
• https://github.com/C2FO/fast-csv/security/advisories/GHSA-8cv5-p934-3hwp
• https://lgtm.com/query/8609731774537641779/
• https://www.npmjs.com/package/%40fast-csv/parse
• https://www.npmjs.com/package/fast-csv

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