CVE-2024-47176

CVE-2024-47176 is a flaw in cups-browsed, the network printer auto-discovery component of the OpenPrinting CUPS printing stack shipped with most major Linux and Unix distributions, which binds to UDP port 631 on all interfaces (INADDR_ANY) and therefore accepts and trusts unauthenticated packets from any source. A remote attacker can send a crafted browse/IPP packet that makes cups-browsed issue a Get-Printer-Attributes IPP request to an attacker-controlled URL. On its own this flaw is rated Medium (5.3), but chained with companion flaws in libcupsfilters (CVE-2024-47076), libppd (CVE-2024-47175), and cups-filters (CVE-2024-47177) it enables unauthenticated arbitrary command execution when a user prints to the attacker's malicious printer; the exposure has also been noted as abusable for DDoS amplification. Any Linux/Unix system running cups-browsed with UDP/631 reachable from an untrusted network is affected. No confirmed widespread in-the-wild exploitation has been reported and the flaw is not yet in CISA's KEV, but public proofs of concept exist and EPSS assigns a ~51% probability of exploitation within 30 days (99th percentile).

What to do: Update cups-browsed and the companion cups-filters/libcupsfilters/libppd packages to the patched releases published by OpenPrinting and your distribution alongside the September 2024 advisories (see GHSA-rj88-6mr5-rcw8). If patched packages are not yet available, stop or disable the cups-browsed service, or firewall inbound UDP port 631 from untrusted networks and ensure it binds only to localhost where network printer discovery is not needed. Audit whether cups-browsed is running and whether UDP/631 is reachable from the internet, and treat any network-reachable CUPS host as a candidate for the full RCE chain.