CVE-2014-7250 in FreeBSD
Summary
by MITRE
The TCP stack in 4.3BSD Net/2, as used in FreeBSD 5.4, NetBSD possibly 2.0, and OpenBSD possibly 3.6, does not properly implement the session timer, which allows remote attackers to cause a denial of service (resource consumption) via crafted packets.
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Analysis
by VulDB Data Team • 06/15/2017
The vulnerability described in CVE-2014-7250 represents a critical flaw in the Transmission Control Protocol implementation across multiple operating systems including FreeBSD 5.4, NetBSD 2.0, and OpenBSD 3.6. This issue stems from improper implementation of the session timer mechanism within the TCP stack, which is a fundamental component responsible for managing connection states and resource allocation. The session timer serves as a crucial mechanism for tracking connection lifecycles and ensuring proper cleanup of resources when connections are terminated or become inactive.
The technical flaw manifests when remote attackers craft specific TCP packets that exploit the inadequate session timer implementation. These malicious packets trigger abnormal behavior in the TCP stack's resource management system, causing the system to consume excessive resources or enter a state where legitimate connections cannot be properly established or maintained. The vulnerability specifically targets the timing mechanisms that govern how long connections remain in memory and how resources are reclaimed after connection termination. This improper handling of session timers creates a condition where the system's resource pool gradually depletes, leading to denial of service conditions that affect the availability of network services.
From an operational perspective, this vulnerability poses significant risks to network infrastructure and service availability. Attackers can leverage this flaw to consume system resources such as memory, file descriptors, and connection tracking entries, effectively rendering the affected system unable to handle legitimate network traffic. The impact extends beyond simple service disruption to potentially compromising the entire network stack's stability, as the TCP implementation is fundamental to all network communications. Systems running these vulnerable versions may experience complete network service degradation, requiring manual intervention or system restarts to restore normal operation. The vulnerability is particularly dangerous in high-traffic environments where resource exhaustion can occur rapidly and systematically.
The mitigation strategies for this vulnerability involve immediate patching of affected systems to update the TCP stack implementations with proper session timer handling. Organizations should prioritize updating their FreeBSD, NetBSD, and OpenBSD systems to versions that contain corrected TCP stack implementations. Network administrators should also implement monitoring solutions to detect unusual resource consumption patterns that may indicate exploitation attempts. Additional defensive measures include configuring firewalls to limit TCP connection rates and implementing intrusion detection systems that can identify suspicious packet patterns targeting the specific vulnerability. According to CWE standards, this vulnerability maps to CWE-129, which addresses improper handling of session timers in network protocols. The ATT&CK framework categorizes this as a resource exhaustion attack technique, specifically targeting system resources through protocol implementation flaws. System administrators should also consider implementing network segmentation and access controls to limit the potential impact of exploitation attempts and reduce the attack surface for such vulnerabilities.