Bug 2545861

Summary:	CVE-2026-105326 cups: cups: argument injection in mailto notifier via notify-recipient-uri [fedora-all]
Product:	[Fedora] Fedora	Reporter:	lcelant
Component:	cups	Assignee:	Zdenek Dohnal <zdohnal>
Status:	NEW ---	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	low	Docs Contact:
Priority:	low
Version:	rawhide	CC:	twaugh, zdohnal
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	{"flaws": ["4797ea0c-fb79-4c76-a88d-81e8b5e5f4c2"]}
Fixed In Version:		Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	2545835

Description lcelant 2026-10-05 10:08:59 UTC

Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

CUPS (Common UNIX Printing System) scheduler accepts IPP Create-Printer-Subscription requests with a notify-recipient-uri attribute. In scheduler/ipp.c, create_printer_subscription validates only the URI scheme (notifier type) and does not validate the recipient address portion of mailto: URIs.

When a subscribed event fires, the mailto notifier in notifier/mailto.c passes the recipient string verbatim as a command-line argument to the configured sendmail binary (pipe_sendmail / execvp) without rejecting leading "-" characters or inserting a "--" separator. A notify-recipient-uri such as mailto:-tC/path/to/crafted.cf is therefore interpreted by traditional sendmail as option arguments (argument injection, CWE-88).

Combined with anonymous Create-Printer-Subscription under default cupsd policy and the ability to stage attacker-controlled files in the CUPS spool via Print-Job, this can chain to arbitrary command execution as the CUPS filter user (lp) when cupsd is network-reachable and a traditional sendmail implementation that honors -C is installed and configured in mailto.conf.

Upstream advisory: GHSA-r4wf-366f-f6g3 (OpenPrinting/cups). Upstream affected version cited: 2.4.7. Upstream fixes on master (1244ed9) and 2.4.x (611d1bd) validate notification email addresses and harden sendmail invocation.

PSIRT ticket: PSIRTSUPT-24443