CVE-2023-27351 in PaperCut
Summary
by MITRE • 04/20/2023
This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability identified as CVE-2023-27351 represents a critical authentication bypass flaw in PaperCut NG version 22.0.5 build 63914. This security weakness resides within the SecurityRequestFilter class, which serves as a fundamental component in the application's access control mechanism. The flaw stems from an improper implementation of the authentication algorithm that fails to properly validate user credentials or session tokens. Attackers can exploit this vulnerability remotely without requiring any valid authentication credentials, effectively allowing unrestricted access to the system's protected resources. The vulnerability's classification as a remote authentication bypass aligns with common attack patterns documented in the ATT&CK framework under the credential access and privilege escalation domains. This type of vulnerability directly undermines the core security model of the application by creating an entry point that circumvents all authentication checks.
The technical implementation of the SecurityRequestFilter class contains a critical flaw in how it processes authentication requests, likely failing to properly validate incoming authentication parameters or by implementing flawed logic that allows unauthorized access. This authentication bypass occurs at the application layer where legitimate authentication mechanisms are either completely bypassed or rendered ineffective due to the flawed implementation. The vulnerability's impact extends beyond simple unauthorized access as it allows attackers to potentially escalate privileges, modify system configurations, or access sensitive data without detection. The fact that this vulnerability was tracked as ZDI-CAN-19226 indicates it was identified through coordinated vulnerability disclosure channels and represents a known security gap that required immediate attention from the vendor and users of the affected software.
Organizations utilizing PaperCut NG 22.0.5 build 63914 face significant operational risks from this vulnerability, as it creates a persistent backdoor that attackers can exploit at any time without requiring valid user credentials. The remote exploit capability means that attackers can target the system from external networks, potentially leading to complete system compromise and data breaches. This vulnerability directly violates security principles outlined in the CWE (Common Weakness Enumeration) catalog, specifically relating to weak authentication mechanisms and improper access control implementations. The attack surface for this vulnerability is broad, as it affects all users of the affected software version and can be exploited by attackers with minimal technical expertise. Organizations should consider this vulnerability as a high-priority threat requiring immediate remediation to prevent potential unauthorized access to critical printing and document management systems.
Immediate mitigation strategies should include applying the vendor-provided security patches or updates as soon as they become available, which typically address the flawed authentication logic in the SecurityRequestFilter class. Organizations should also implement network-level restrictions and monitoring to detect suspicious authentication attempts or unauthorized access patterns. The vulnerability's classification as a remote authentication bypass requires defensive measures such as network segmentation, firewall rules, and intrusion detection systems to prevent exploitation. Additionally, security teams should conduct comprehensive vulnerability assessments to identify any potential unauthorized access that may have occurred before the patch was applied. The remediation process should also include reviewing access controls, monitoring user activities, and ensuring that all authentication mechanisms function properly after patching. This vulnerability demonstrates the critical importance of proper authentication implementation and the potential consequences when such mechanisms fail, making it essential for organizations to maintain updated security practices and rapid response capabilities to address similar threats.