A malicious or attacker-controlled IPP printer can return a crafted text printer-status attribute, such as marker-message, containing embedded newline characters. The CUPS ipp backend reports this remote printer attribute to the scheduler through the backend stderr/status stream. The current quoting helper escapes quotes and backslashes, but it does not reject or encode LF/CR. As a result, attacker-controlled printer status text can create a new backend status line beginning with PPD:.

NOTE: https://github.com/OpenPrinting/cups/security/advisories/GHSA-7hqf-mfhx-7r3v
NOTE: Fixed by: https://github.com/OpenPrinting/cups/commit/d41cf0616688721e9d435d54118c4c8a36ed596a (v2.4.20)