CVE-2010-2432 in cups
Summary
by MITRE
The cupsDoAuthentication function in auth.c in the client in CUPS before 1.4.4, when HAVE_GSSAPI is omitted, does not properly handle a demand for authorization, which allows remote CUPS servers to cause a denial of service (infinite loop) via HTTP_UNAUTHORIZED responses.
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Analysis
by VulDB Data Team • 09/18/2021
The vulnerability identified as CVE-2010-2432 affects the Common Unix Printing System (CUPS) version 1.4.3 and earlier, specifically within the client-side authentication handling mechanism. This issue resides in the cupsDoAuthentication function located in the auth.c source file, where the absence of proper authorization handling creates a critical security flaw that can be exploited by remote attackers. The vulnerability becomes particularly dangerous when the HAVE_GSSAPI compilation flag is omitted, which is common in many production environments where GSSAPI support is not required or available. The flaw represents a classic case of improper input validation and error handling that can lead to system instability and service disruption.
The technical implementation of this vulnerability stems from the client's inability to properly process HTTP_UNAUTHORIZED responses when authentication is required. When a CUPS client connects to a malicious server that demands authentication, the authentication function fails to recognize that the server is requesting authorization rather than responding to an authentication failure. This misinterpretation causes the client to enter an infinite loop where it continuously attempts to authenticate without proper state management or timeout mechanisms. The authentication process becomes trapped in a recursive pattern that consumes system resources and prevents normal operation, effectively creating a denial of service condition that can be triggered remotely without any authentication requirements from the attacker's side.
From an operational perspective, this vulnerability poses significant risks to printing infrastructure and network availability. Organizations relying on CUPS for print management services face potential disruption of their printing capabilities when connected to malicious or compromised servers. The infinite loop behavior can exhaust system resources including CPU cycles, memory, and network connections, potentially affecting multiple concurrent print jobs or even entire print queues. The remote nature of the attack means that an attacker can exploit this vulnerability without requiring physical access or prior authentication credentials, making it particularly dangerous in networked environments where CUPS clients might connect to untrusted servers. This vulnerability directly impacts the availability aspect of the CIA triad and can be classified under CWE-835, which deals with infinite loops or infinite recursions, specifically in the context of authentication handling.
The exploitation of this vulnerability aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to denial of service attacks and credential access. Attackers can leverage this weakness to perform service disruption attacks against printing infrastructure, potentially affecting business operations and productivity. The vulnerability also represents a privilege escalation vector in certain contexts where print servers might be used to access other network resources. Organizations should consider this vulnerability in their threat modeling exercises, especially in environments where CUPS clients might connect to untrusted or potentially compromised servers. The lack of proper error handling and state management in the authentication flow demonstrates a failure to implement robust input validation practices that are fundamental to secure software development.
Mitigation strategies for CVE-2010-2432 include immediate patching of CUPS installations to version 1.4.4 or later, where the authentication handling has been corrected to properly process HTTP_UNAUTHORIZED responses. System administrators should also implement network segmentation to limit exposure of CUPS clients to untrusted servers and consider implementing authentication requirements for all CUPS server connections. Additional defensive measures include monitoring for unusual authentication patterns and implementing resource limits on print client processes to prevent complete system exhaustion. Organizations should also review their compilation configurations to ensure that appropriate security features are enabled and that unnecessary compilation flags are not omitted. The vulnerability highlights the importance of proper state management in authentication protocols and demonstrates how seemingly minor implementation flaws can create significant security risks in networked systems.