CVE-2014-8475 in FreeBSD
Summary
by MITRE
FreeBSD 9.1, 9.2, and 10.0, when compiling OpenSSH with Kerberos support, uses incorrect library ordering when linking sshd, which causes symbols to be resolved incorrectly and allows remote attackers to cause a denial of service (sshd deadlock and prevention of new connections) by ending multiple connections before authentication is completed.
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Analysis
by VulDB Data Team • 02/24/2022
The vulnerability identified as CVE-2014-8475 represents a critical flaw in the FreeBSD operating system's handling of OpenSSH compilation processes when Kerberos authentication support is enabled. This issue affects FreeBSD versions 9.1, 9.2, and 10.0, creating a scenario where the build process generates an executable with incorrect library linking order. The fundamental problem lies in how the linker resolves symbols during the compilation of the sshd daemon, specifically when Kerberos libraries are involved in the build chain. This improper symbol resolution creates a condition where the sshd service becomes susceptible to specific attack patterns that can lead to complete service disruption.
The technical flaw manifests through incorrect library ordering during the linking phase of OpenSSH compilation when Kerberos support is enabled. When the build system processes the compilation flags and library dependencies, it fails to properly order the library references, causing the linker to resolve symbols from the wrong library versions. This misordering creates a dependency chain where critical functions required for proper sshd operation become unresolved or resolved to incorrect implementations. The vulnerability specifically impacts the sshd daemon's ability to handle concurrent connections properly, particularly when dealing with multiple connection attempts that terminate before authentication completes.
The operational impact of this vulnerability is severe and directly affects the availability of SSH services on affected FreeBSD systems. Remote attackers can exploit this flaw by initiating multiple connection attempts to the sshd service and then terminating these connections before the authentication process completes. This specific attack pattern triggers a deadlock condition within the sshd daemon, causing it to become unresponsive and unable to accept new connections. The service essentially enters a state where it cannot properly manage its connection handling loop, leading to complete denial of service for legitimate users attempting to establish SSH sessions. This vulnerability undermines the fundamental availability guarantee that SSH services should provide, making it particularly dangerous in production environments where continuous access is critical.
The attack vector for this vulnerability aligns with the ATT&CK framework's privilege escalation and denial of service techniques, specifically targeting the service availability aspect of system security. From a CWE perspective, this represents a classic case of improper library linking and symbol resolution, falling under CWE-119 for memory corruption and CWE-476 for null pointer dereference conditions that can occur during improper symbol resolution. The vulnerability demonstrates how seemingly minor build configuration issues can create significant security implications when they affect core system services. Organizations running FreeBSD systems with OpenSSH and Kerberos support should immediately apply the relevant patches or updates to address this issue, as the vulnerability can be exploited remotely without requiring authentication credentials. The fix typically involves correcting the library linking order during the build process to ensure proper symbol resolution and prevent the deadlock conditions that allow the denial of service attack to succeed.
This vulnerability highlights the importance of proper build system configuration and library dependency management in security-critical applications. The issue serves as a reminder that even well-established software packages can contain build-time flaws that create runtime security vulnerabilities. System administrators should implement regular security audits of their build environments and ensure that all security patches are applied promptly to prevent exploitation of such issues. The vulnerability also underscores the need for comprehensive testing of compiled software, particularly in security-sensitive contexts where improper linking can create exploitable conditions that affect system availability and service integrity.