Vulnerability identifier: #VU55488

Vulnerability risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-31810

CWE-ID: CWE-200

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Ruby
Universal components / Libraries / Scripting languages

Vendor: Ruby

Description

The vulnerability allows a remote attacker to gain access to potentially sensitive information.

The vulnerability exists within Net::FTP in Ruby when processing PASV responses. A remote attacker can trick the victim to connect to a malicious FTP server and 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).

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Ruby: 2.6.0 - 3.0.1

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External links
http://www.ruby-lang.org/en/news/2021/07/07/trusting-pasv-responses-in-net-ftp/
http://hackerone.com/reports/1145454
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MWXHK5UUHVSHF7HTHMX6JY3WXDVNIHSL/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.