CVE-2020-26256
Denial of service in fast-csv
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Denial of service in fast-csv
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.
- Record
CVE-2020-26256- CVSS 3.1
- 5.7 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-400
- Updated
- 2026-11-02
EUVDEUVD-2020-1489
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.
- Record
EUVD-2020-1489- CVSS 3.1
- 5.7 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-8cv5-p934-3hwp
Denial of service in fast-csv
Impact
Possible ReDoS (Regular Expression Denial of Service) when using ignoreEmpty option when parsing.
Patches
This has been patched in v4.3.6
Workarounds
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
References
This vulnerability was found using a CodeQL query which identified EMPTY_ROW_REGEXP regular expression as vulnerable.
Link to query run.
For more information
If you have any questions or comments about this advisory:
- Open an issue in fast-csv
- Record
GHSA-8cv5-p934-3hwp- CVSS 3.1
- 5.7 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-400
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2020-26256- CVSS 3.1
- 5.7 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 3.5 Low
AV:N/AC:M/Au:S/C:N/I:N/A:P - Weakness
- CWE-400
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2020-26256- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVGHSA-8cv5-p934-3hwp
Denial of service in fast-csv
Impact
Possible ReDoS (Regular Expression Denial of Service) when using ignoreEmpty option when parsing.
Patches
This has been patched in v4.3.6
Workarounds
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
References
This vulnerability was found using a CodeQL query which identified EMPTY_ROW_REGEXP regular expression as vulnerable.
Link to query run.
For more information
If you have any questions or comments about this advisory:
- Open an issue in fast-csv
- Record
GHSA-8cv5-p934-3hwp- CVSS 3.1
- 5.7 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-400
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
fast-csvnpm |
before 4.3.6 | 4.3.6 |
@fast-csv/parsenpm |
before 4.3.6 | 4.3.6 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-26256 is a medium vulnerability (CVSS 5.7) in C2fo Fast-csv, published December 8, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.54%, the 74th percentile. Fixed in fast-csv 4.3.6.