CVE-2008-2285 in Linux
Summary
by MITRE
The ssh-vulnkey tool on Ubuntu Linux 7.04, 7.10, and 8.04 LTS does not recognize authorized_keys lines that contain options, which makes it easier for remote attackers to exploit CVE-2008-0166 by guessing a key that was not identified by this tool.
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Analysis
by VulDB Data Team • 08/01/2021
The vulnerability described in CVE-2008-2285 pertains to a critical flaw in the ssh-vulnkey tool functionality within specific Ubuntu Linux versions including 7.04, 7.10, and 8.04 LTS. This issue represents a significant security weakness that directly impacts the detection and mitigation of known vulnerable SSH keys. The tool's inability to properly parse authorized_keys files containing options creates a false sense of security for system administrators who rely on this utility for vulnerability assessment. The flaw operates at the intersection of cryptographic key management and security auditing, where proper key validation becomes compromised due to incomplete parsing logic.
The technical implementation of this vulnerability stems from the ssh-vulnkey tool's failure to correctly interpret SSH key configuration lines that include options such as command, environment, or other directive parameters. When authorized_keys entries contain these options, the tool's parsing mechanism fails to recognize that a particular key might be vulnerable to CVE-2008-0166, which specifically addresses weak SSH key generation practices. This parsing deficiency creates a false positive scenario where potentially compromised keys remain undetected, allowing attackers to exploit the vulnerability through key guessing techniques. The flaw essentially bypasses the intended security controls designed to identify and warn about known vulnerable key patterns.
The operational impact of this vulnerability extends beyond simple detection failure to create a substantial attack surface for remote adversaries. Attackers can exploit the gap in key validation by crafting key guessing strategies that target vulnerable keys which the ssh-vulnkey tool would not identify. This weakness particularly affects systems where administrators depend on automated tools for security auditing, as the false negatives generated by this tool could lead to prolonged exposure to known vulnerabilities. The vulnerability directly relates to CWE-20: Improper Input Validation, where the tool fails to properly validate and parse input data from SSH configuration files, and aligns with ATT&CK technique T1562.006: Impair Defenses - Indicator Removal from Tools, as it creates false indicators that mask actual security issues.
The mitigation approach requires immediate system updates to patched versions of the ssh-vulnkey tool or alternative key validation methods that properly handle SSH key options. System administrators should implement manual verification processes for SSH key configurations, particularly focusing on authorized_keys files that contain option parameters. Additionally, organizations should consider implementing comprehensive key management policies that include regular manual audits of SSH configurations, as automated tools may not provide complete coverage of all potential vulnerabilities. The vulnerability demonstrates the critical importance of robust input parsing in security tools and highlights the need for thorough testing of security utilities against various configuration scenarios to ensure effective protection against known threats.