CVE-2004-2338 in OpenBSD
Summary
by MITRE
OpenBSD 3.3 and 3.4 does not properly parse Accept and Deny rules without netmasks on big-endian 64-bit platforms such as SPARC64, which may allow remote attackers to bypass access restrictions.
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Analysis
by VulDB Data Team • 06/28/2018
The vulnerability identified as CVE-2004-2338 represents a critical flaw in the OpenBSD 3.3 and 3.4 firewall implementation that specifically affects big-endian 64-bit architectures such as SPARC64. This issue stems from improper parsing of access control rules that lack netmask specifications, creating a significant security gap in network access control mechanisms. The flaw manifests exclusively on systems using big-endian byte order with 64-bit processors, making it architecture-specific and potentially overlooked in security assessments targeting other platforms.
The technical root cause of this vulnerability lies in how the OpenBSD firewall subsystem handles rule parsing when netmasks are omitted from Accept and Deny directives. In standard network security implementations, when a netmask is not explicitly specified in an access control rule, the system typically defaults to a full mask or applies appropriate default values to ensure proper access control behavior. However, on big-endian 64-bit platforms, the parsing logic fails to correctly interpret these implicit netmask values, leading to malformed rule evaluation that can result in unintended access permissions.
This vulnerability operates at the network security layer and directly impacts the integrity of access control policies implemented through OpenBSD's packet filtering system. The flaw allows remote attackers to bypass intended access restrictions by exploiting the improper rule parsing behavior, potentially enabling unauthorized network access to systems protected by these firewall rules. The security implications extend beyond simple access bypass, as this could allow attackers to circumvent multiple layers of network security controls that depend on proper rule enforcement.
The operational impact of CVE-2004-2338 is significant for organizations running OpenBSD 3.3 or 3.4 on SPARC64 platforms, as it effectively undermines the firewall's ability to enforce access control policies. Systems affected by this vulnerability may experience unauthorized network connections, data exfiltration attempts, or other malicious activities that exploit the bypassed access restrictions. The architecture-specific nature of the vulnerability means that organizations using different processor architectures or newer OpenBSD versions are not affected, but those running the vulnerable versions on SPARC64 systems face immediate security risks.
Security mitigations for this vulnerability require immediate patching of affected OpenBSD systems to versions that contain the corrected rule parsing logic. Organizations should also implement additional network monitoring to detect potential exploitation attempts and review existing firewall rules to ensure proper netmask specification for all access control entries. The fix addresses the core parsing issue by ensuring consistent rule evaluation across all supported architectures, aligning with best practices for secure network configuration management. This vulnerability demonstrates the importance of thorough testing across different hardware architectures when implementing security controls, as platform-specific behaviors can introduce unexpected security weaknesses that may not be apparent during standard security assessments.
The vulnerability aligns with CWE-125, which addresses out-of-bounds read conditions that can lead to access control bypasses, and relates to ATT&CK technique T1071.004 for application layer protocol usage in network communications. This represents a classic example of how low-level implementation details in security-critical systems can create exploitable weaknesses that bypass higher-level security controls. The issue highlights the necessity of comprehensive testing across all supported platforms and architectures, particularly when implementing security-sensitive components that directly impact network access control policies.