CVE-2021-31810

Name: CVE-2021-31810
Creator: NVD / NIST
Published: 2021-07-13T13:15:09.243+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.8/10EPSS 3.05%

Last modified Jun 17, 2026

CVE-2021-31810 is a medium-severity vulnerability rated 5.8/10 on the CVSS scale. An issue was discovered in Ruby through 2.6.7, 2.7.x through 2.7.3, and 3.x through 3.0.1. A malicious FTP server can use the PASV response to trick Net::FTP into connecting back to a given IP address and port. EPSS estimates a 3.05% chance of exploitation in the next 30 days.

Description

An issue was discovered in Ruby through 2.6.7, 2.7.x through 2.7.3, and 3.x through 3.0.1. A malicious FTP server can use the PASV response to trick Net::FTP into connecting back to a given IP address and port. This potentially makes curl extract information about services that are otherwise private and not disclosed (e.g., the attacker can conduct port scans and service banner extractions).

Metrics

CVSS 3.1

5.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

EPSS Probability

3.05%

85.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Ruby-Lang	Ruby	<= 2.6.7
Ruby-Lang	Ruby	>= 2.7.0, <= 2.7.3
Ruby-Lang	Ruby	>= 3.0.0, <= 3.0.1
Debian	Debian Linux	9.0
Oracle	Jd Edwards Enterpriseone Tools	< 9.2.6.1

References

https://hackerone.com/reports/1145454Exploit, Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/10/msg00009.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/04/msg00033.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MWXHK5UUHVSHF7HTHMX6JY3WXDVNIHSL/
https://security.gentoo.org/glsa/202401-27
https://security.netapp.com/advisory/ntap-20210917-0001/Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
https://www.ruby-lang.org/en/news/2021/07/07/trusting-pasv-responses-in-net-ftp/Vendor Advisory
https://hackerone.com/reports/1145454Exploit, Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/10/msg00009.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/04/msg00033.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MWXHK5UUHVSHF7HTHMX6JY3WXDVNIHSL/
https://security.gentoo.org/glsa/202401-27
https://security.netapp.com/advisory/ntap-20210917-0001/Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
https://www.ruby-lang.org/en/news/2021/07/07/trusting-pasv-responses-in-net-ftp/Vendor Advisory

Timeline

Published: Jul 13, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-31810?

How severe is CVE-2021-31810?

CVE-2021-31810 has a CVSS score of 5.8/10 (MEDIUM severity). The EPSS model estimates a 3.05% probability of exploitation in the next 30 days.

How do I fix CVE-2021-31810?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-31810?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST