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Fencer Vulns
medium 5.7

CVE-2020-26256 json

Denial of service in fast-csv

published 2020-12-08 5 y ago modified 2026-09-10 1 mo ago also GHSA-8cv5-p934-3hwp , EUVD-2020-1489

cvss
5.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 75%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm fast-csv 4.3.6
  • npm @fast-csv/parse 4.3.6
  • c2fo fast-csv 4.3.6

Exploit prediction

1.54% chance of exploitation in the next 30 days, higher than 75% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • lgtm.com https://lgtm.com/query/8609731774537641779/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 3.5 AV:N/AC:M/Au:S/C:N/I:N/A:P
GitHub 3.1 5.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm fast-csv
<4.3.6
4.3.6
npm @fast-csv/parse
<4.3.6
4.3.6

Affected products

  • C2FO fast-csv

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.