CVE-2015-8560 in cups-filters
Summary
by MITRE
Incomplete blacklist vulnerability in util.c in foomatic-rip in cups-filters 1.0.42 before 1.4.0 and in foomatic-filters in Foomatic 4.0.x allows remote attackers to execute arbitrary commands via a ; (semicolon) character in a print job, a different vulnerability than CVE-2015-8327.
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Analysis
by VulDB Data Team • 07/24/2022
The vulnerability described in CVE-2015-8560 represents a critical command injection flaw within the foomatic-rip component of the cups-filters package and foomatic-filters software suite. This issue affects versions prior to 1.4.0 in cups-filters and version 4.0.x in foomatic-filters, creating a significant security risk for systems that process print jobs through these components. The vulnerability stems from an incomplete blacklist implementation that fails to properly sanitize user input containing semicolon characters, which are commonly used in shell command execution contexts.
The technical flaw exists in the util.c file where the foomatic-rip utility processes print job data. When a print job contains a semicolon character, the system does not adequately filter or escape this input before passing it to underlying shell commands. This incomplete blacklist approach means that while some dangerous characters may be blocked, the semicolon character specifically is not properly handled, allowing attackers to inject malicious commands that execute with the privileges of the printing service. The vulnerability operates at the application layer and specifically targets the print processing pipeline where user-supplied data is interpreted as command parameters rather than simple data.
The operational impact of this vulnerability is severe as it enables remote attackers to execute arbitrary commands on affected systems without requiring authentication or local access. An attacker can submit a specially crafted print job containing a semicolon followed by malicious shell commands, which then get executed by the print processing system. This creates a potential attack vector for privilege escalation, data exfiltration, system compromise, and denial of service conditions. The vulnerability is particularly dangerous in networked printing environments where multiple users can submit print jobs, as it allows for unauthorized command execution on the print server itself. This type of vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and represents a classic command injection attack pattern.
Mitigation strategies for this vulnerability involve upgrading to affected software versions that contain proper input sanitization and complete blacklist implementations. System administrators should immediately apply patches to cups-filters version 1.4.0 or later and foomatic-filters version 4.0.1 or later where the vulnerability has been addressed. Additionally, network segmentation and access controls should be implemented to limit exposure of print services to untrusted networks. Input validation should be strengthened to properly escape or remove semicolon characters and other special shell metacharacters from print job data. Organizations should also consider implementing monitoring solutions to detect unusual print job patterns that might indicate exploitation attempts, as this vulnerability can be leveraged for persistent access to systems through the print processing infrastructure. The remediation approach should follow established security practices outlined in the ATT&CK framework for command and scripting interpreter techniques, specifically targeting the execution of malicious code through print services and system utilities.