CVE-2009-0870 in Solaris
Summary
by MITRE
The NFSv4 Server module in the kernel in Sun Solaris 10, and OpenSolaris before snv_111, allow local users to cause a denial of service (infinite loop and system hang) by accessing an hsfs filesystem that is shared through NFSv4, related to the rfs4_op_readdir function.
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Analysis
by VulDB Data Team • 04/21/2025
The vulnerability described in CVE-2009-0870 represents a critical denial of service flaw within the Network File System version 4 implementation of Sun Solaris operating systems. This issue specifically affects the kernel-level NFSv4 server module and manifests when a local user attempts to access a hsfs filesystem that has been exported through NFSv4. The hsfs filesystem, which stands for High Sierra File System, is typically used for optical disc images and is commonly encountered in Unix-like systems. The vulnerability arises from improper handling of directory read operations within the NFSv4 server implementation, creating a scenario where the system becomes unresponsive due to an infinite loop in the rfs4_op_readdir function.
The technical root cause of this vulnerability lies in the insufficient input validation and error handling mechanisms within the NFSv4 server code. When the rfs4_op_readdir function processes directory listing requests for hsfs filesystems, it fails to properly validate the filesystem structure or handle edge cases that could lead to recursive or circular references. This flaw allows a local attacker to craft specific directory access patterns that trigger the infinite loop condition, causing the system to consume excessive CPU resources and eventually become unresponsive. The vulnerability is particularly concerning because it can be exploited by any local user with access to the system, making it a significant security risk in multi-user environments where privilege escalation is not required.
From an operational perspective, this vulnerability poses a substantial threat to system availability and reliability in Solaris environments. The infinite loop condition results in complete system hang, effectively rendering the affected server unusable until manual intervention occurs through system reboot. This type of denial of service attack can have cascading effects in enterprise environments where Solaris servers are critical infrastructure components, potentially disrupting business operations and requiring immediate incident response procedures. The vulnerability affects a wide range of Solaris versions including Solaris 10 and various OpenSolaris builds prior to snv_111, indicating it was present across multiple releases and likely impacted numerous production systems.
The impact of this vulnerability aligns with CWE-835, which specifically addresses the issue of infinite loops in software implementations. From an attack methodology standpoint, this vulnerability can be classified under the MITRE ATT&CK framework's privilege escalation and denial of service categories, as it allows local users to achieve system-level disruption without requiring elevated privileges. The exploitation process is relatively straightforward for local attackers who understand the filesystem structure and can construct the appropriate access patterns to trigger the loop condition. Organizations should consider implementing monitoring solutions to detect unusual CPU consumption patterns that might indicate exploitation attempts, as the vulnerability does not require network access and operates entirely within the local system context.
Mitigation strategies for this vulnerability should include immediate patch application from Oracle, which would contain the specific code modifications needed to fix the rfs4_op_readdir function implementation. System administrators should prioritize patching affected systems, particularly those running older Solaris releases where the vulnerability is known to exist. Additionally, implementing proper access controls and limiting local user privileges can reduce the attack surface, though this does not prevent exploitation by users with existing access to the system. Network segmentation and monitoring solutions should be deployed to detect anomalous behavior patterns that might indicate exploitation attempts, while regular system audits can help identify systems that may have been compromised or are running vulnerable software versions. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain inventory tracking of all Solaris installations to identify potentially vulnerable systems throughout their infrastructure.