CVE-2013-5691 in FreeBSD
Summary
by MITRE
The (1) IPv6 and (2) ATM ioctl request handlers in the kernel in FreeBSD 8.3 through 9.2-STABLE do not validate SIOCSIFADDR, SIOCSIFBRDADDR, SIOCSIFDSTADDR, and SIOCSIFNETMASK requests, which allows local users to perform link-layer actions, cause a denial of service (panic), or possibly gain privileges via a crafted application.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 05/24/2021
The vulnerability identified as CVE-2013-5691 represents a critical security flaw in the FreeBSD kernel's network interface handling mechanisms, specifically affecting versions 8.3 through 9.2-STABLE. This issue resides within the kernel's IPv6 and ATM ioctl request handlers, where insufficient input validation creates pathways for malicious exploitation. The vulnerability stems from the failure to properly validate several critical network interface configuration requests including SIOCSIFADDR for setting interface addresses, SIOCSIFBRDADDR for broadcast addresses, SIOCSIFDSTADDR for destination addresses, and SIOCSIFNETMASK for network masks. These ioctl commands are fundamental to network interface management and typically require strict validation to prevent unauthorized modifications to system networking parameters.
The technical exploitation of this vulnerability occurs through local users who can craft malicious applications to manipulate these unvalidated network interface requests. When the kernel processes these malformed requests without proper validation, it can lead to unpredictable behavior including kernel panics that result in system crashes and denial of service conditions. The lack of proper input sanitization means that attackers can potentially bypass normal access controls and execute unauthorized link-layer operations that should only be permitted through legitimate system administration channels. This vulnerability falls under the CWE-119 category of "Improper Restriction of Operations within the Bounds of a Memory Buffer" and represents a classic example of insufficient input validation that can escalate to privilege escalation or system compromise.
The operational impact of CVE-2013-5691 extends beyond simple denial of service scenarios, as local users with minimal privileges can potentially leverage this weakness to gain elevated system access. The kernel panic conditions caused by malformed ioctl requests can be particularly disruptive in production environments where system stability is paramount, potentially leading to complete service outages. Attackers can exploit this vulnerability to cause system instability, which may be used as a vector for more sophisticated attacks or to establish persistent access through privilege escalation. The vulnerability's classification aligns with ATT&CK technique T1068 which covers "Exploitation for Privilege Escalation" and T1499 which covers "Endpoint Denial of Service" within the adversary tactics framework. Organizations running affected FreeBSD versions face significant risk, particularly in environments where local user access cannot be strictly controlled.
Mitigation strategies for CVE-2013-5691 require immediate patching of affected FreeBSD systems to the latest stable releases that contain the necessary kernel fixes for proper ioctl validation. System administrators should implement strict access controls to limit local user privileges and monitor for unusual network interface modifications that might indicate exploitation attempts. Network segmentation and monitoring solutions should be deployed to detect anomalous ioctl activity patterns that could signal exploitation of this vulnerability. The fix implemented by FreeBSD developers involved adding proper input validation checks to the IPv6 and ATM ioctl handlers, ensuring that all network interface configuration requests are properly sanitized before processing. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain comprehensive system monitoring to detect any exploitation attempts. Regular security audits of kernel components and network interface configurations should be conducted to identify similar validation weaknesses that could present analogous risks.