Bug 2545835 (CVE-2026-105326)

Summary:	CVE-2026-105326 cups: cups: argument injection in mailto notifier via notify-recipient-uri
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers, zdohnal
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Doc Text:	An argument injection flaw was found in CUPS. When email notification is configured, the CUPS scheduler accepts printer subscription requests that supply a mailto notify-recipient-uri. The mailto notifier passes the recipient address to the configured sendmail program without ensuring it cannot be interpreted as command-line options. A remote attacker who can reach the CUPS service could supply a crafted recipient value starting with "-" to influence sendmail behavior. Successful exploitation depends on the installed mail transfer agent and CUPS network exposure, and may lead to execution of attacker-controlled commands with the privileges of the CUPS service user.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2545861
Bug Blocks:

Description OSIDB Bzimport 2026-10-05 08:48:54 UTC

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