CVE-2020-26256: Denial of Service in fast-csv
Summary
CVE-2020-26256: Denial of service in fast-csv. Affects fast-csv versions < 4.3.6. Fixed in 4.3.6. How to fix ↓
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Background
fast-csv is an npm package that provides a high-performance CSV parser and formatter for Node.js. It allows users to parse and format CSV data efficiently. However, a vulnerability has been discovered in fast-csv that can lead to a denial of service (DoS) attack. This vulnerability affects versions prior to v4.3.6 of the fast-csv package and the @fast-csv/parse package.
Vulnerability Detail
The vulnerability, identified as CVE-2020-26256, is a possible ReDoS (Regular Expression Denial of Service) when using the ignoreEmpty option during parsing. This vulnerability can be exploited by an attacker to cause a DoS condition by providing specially crafted input that triggers excessive backtracking in the regular expression used by the ignoreEmpty option. The impact of this vulnerability can result in a significant slowdown or unresponsiveness of the application.
How To Fix
Latest published version: 5.0.8 as of 23 Oct 2026
npm install fast-csv@5.0.8Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
4.3.6
This is the first release that contains the fix.
npm install fast-csv@4.3.6Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If you are using the ignoreEmpty parsing option and cannot immediately upgrade to the latest version, a workaround is to avoid using the ignoreEmpty option or to sanitize the input data to prevent the triggering of excessive backtracking. However, it is strongly advised to upgrade to the patched version as soon as possible.
Conclusion
The vulnerability in fast-csv (CVE-2020-26256) can lead to a denial of service (DoS) attack. It is crucial to upgrade to the latest version (v4.3.6) of the fast-csv package or the @fast-csv/parse package to mitigate the risk. If you have any further questions or need assistance with vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for fast-csv →
FAQ
fast-csv is an npm package that provides a high-performance CSV parser and formatter for Node.js. It allows users to efficiently parse and format CSV data.
The vulnerability can lead to a denial of service (DoS) condition in applications using fast-csv. It can cause a significant slowdown or unresponsiveness of the application.
To fix this vulnerability, you should upgrade to the latest version of the fast-csv package (v4.3.6) or the @fast-csv/parse package.
If you cannot immediately upgrade, you can avoid using the ignoreEmpty option or sanitize the input data to prevent excessive backtracking. However, upgrading to the patched version is strongly recommended.
You can find more information about this vulnerability in the GitHub advisory for GHSA-8cv5-p934-3hwp.
