CVE-2015-0885 in Checkpw
Summary
by MITRE
checkpw 1.02 and earlier allows remote attackers to cause a denial of service (infinite loop) via a -- (dash dash) in a username.
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Analysis
by VulDB Data Team • 12/01/2024
The vulnerability identified as CVE-2015-0885 affects checkpw version 1.02 and earlier, representing a critical denial of service weakness that can be exploited by remote attackers to disrupt system availability. This flaw specifically manifests when the application processes username inputs containing double dashes, creating an infinite loop condition that consumes system resources and prevents legitimate authentication requests from being processed. The issue stems from inadequate input validation and improper handling of special characters within the authentication framework, making it particularly dangerous in environments where authentication services are critical to system operations.
The technical implementation of this vulnerability occurs within the username parsing logic of the checkpw utility, where the presence of double dashes triggers a malformed state in the processing loop. When the system encounters a username containing -- characters, the internal state machine becomes trapped in an infinite iteration pattern, continuously reprocessing the same input without progressing toward authentication completion. This behavior aligns with CWE-835, which specifically addresses infinite loops or iterations that can lead to denial of service conditions. The flaw demonstrates poor input sanitization practices and lacks proper boundary checks that would normally prevent such malformed data from causing system instability.
From an operational perspective, this vulnerability presents significant risk to authentication services and can be exploited by malicious actors to create sustained denial of service conditions against systems relying on checkpw for user validation. Attackers can leverage this weakness by submitting specially crafted usernames containing double dashes to any service that utilizes checkpw for authentication, resulting in resource exhaustion and service unavailability. The impact extends beyond simple service disruption as it can affect cascading system dependencies, potentially leading to broader availability issues within networked environments. This vulnerability particularly affects Unix-like systems and applications that depend on traditional authentication mechanisms, making it relevant to enterprise environments where legacy authentication systems remain in use.
Security mitigations for CVE-2015-0885 should prioritize immediate patching of affected checkpw versions to 1.03 or later, which contain the necessary input validation fixes. Organizations should implement additional defensive measures including input filtering at network boundaries, rate limiting for authentication requests, and monitoring for anomalous username patterns containing special characters. The remediation process must include thorough testing of patched systems to ensure that legitimate authentication workflows remain functional while the denial of service condition is eliminated. Network segmentation and access controls should be reviewed to limit exposure of vulnerable systems to untrusted networks, aligning with ATT&CK technique T1499.1 which addresses network denial of service attacks. System administrators should also establish monitoring protocols to detect and respond to potential exploitation attempts, ensuring that any occurrence of this vulnerability can be rapidly identified and addressed to maintain service availability and system integrity.