CVE-2006-5550 in FreeBSD
Summary
by MITRE
The kernel in FreeBSD 6.1 and OpenBSD 4.0 allows local users to cause a denial of service via unspecified vectors involving certain ioctl requests to /dev/crypto.
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Analysis
by VulDB Data Team • 04/25/2026
The vulnerability identified as CVE-2006-5550 represents a critical denial of service weakness within the cryptographic subsystem of FreeBSD 6.1 and OpenBSD 4.0 operating systems. This issue manifests through unspecified vectors that specifically target ioctl requests directed to the /dev/crypto device interface, which serves as the primary communication channel for cryptographic operations within these Unix-like systems. The affected kernel components handle various cryptographic functions including encryption, decryption, and key management through this dedicated device file, making it a prime target for exploitation by local attackers who possess minimal system privileges.
The technical flaw stems from inadequate input validation and error handling within the kernel's cryptographic ioctl implementation. When maliciously crafted ioctl requests are sent to /dev/crypto, the kernel fails to properly validate the parameters or handle exceptional conditions, leading to potential kernel crashes or system lockups. This vulnerability operates at the kernel level where the device driver processes cryptographic operations, making it particularly dangerous as it can compromise the entire system stability. The unspecified nature of the exact vectors suggests that multiple attack paths exist within the ioctl handling code, potentially affecting different cryptographic algorithms or operations within the subsystem. Such weaknesses often originate from improper memory management, buffer overflows, or race conditions that occur during the processing of cryptographic requests.
The operational impact of this vulnerability extends beyond simple system unavailability as it can result in complete system crashes requiring manual reboot or automated recovery mechanisms. Local users who can access the /dev/crypto device interface can exploit this weakness to deny service to legitimate system operations, potentially affecting critical cryptographic services such as SSL/TLS operations, file encryption, and secure communication protocols. The attack requires only local privileges, making it particularly concerning as it can be exploited by malicious users already within the system or by attackers who have gained limited access through other means. This vulnerability directly impacts the availability and reliability of cryptographic services, which are fundamental to system security and data protection mechanisms.
Mitigation strategies for CVE-2006-5550 should prioritize immediate system updates and patches provided by FreeBSD and OpenBSD security teams. System administrators should implement strict access controls on the /dev/crypto device to limit which users or processes can interact with it, although this approach provides only partial protection as the vulnerability exists within kernel space. The implementation of proper input validation and error handling within kernel cryptographic modules represents the most effective long-term solution. Organizations should also consider monitoring for suspicious ioctl activity patterns and implementing intrusion detection systems that can identify potential exploitation attempts. This vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and may relate to ATT&CK technique T1499.004 for network denial of service attacks. Regular system audits and kernel security assessments should be conducted to identify similar weaknesses in other cryptographic subsystems, as such vulnerabilities often indicate broader security architecture issues that require comprehensive remediation approaches.