A malicious server can use the PASV response to trick curl into connecting back to a given IP address and port, and this way potentially make curl extract information about services that are otherwise private and not disclosed, for example doing port scanning and service banner extractions. If curl operates on a URL provided by a user (which by all means is an unwise setup), a user can exploit that and pass in a URL to a malicious FTP server instance without needing any server breach to perform the attack.

A vulnerability found in curl. This security flaw happens when curl is used to retrieve and parse cookies from an HTTP(S) server, where it accepts cookies using control codes (byte values below 32), and also when cookies that contain such control codes are later sent back to an HTTP(S) server, possibly causing the server to return a 400 response. This issue effectively allows a "sister site" to deny service to siblings and cause a denial of service attack.

A privacy issue was addressed with improved private data redaction for log entries. This issue is fixed in macOS Ventura 13.3, iOS 16.4 and iPadOS 16.4, iOS 15.7.4 and iPadOS 15.7.4, tvOS 16.4, watchOS 9.4, macOS Big Sur 11.7.5. An app may be able to access information about a user’s contacts.