CVE-2006-0047 in Freeciv
Summary
by MITRE
packets.c in Freeciv 2.0 before 2.0.8 allows remote attackers to cause a denial of service (server crash) via crafted packets with negative compressed size values.
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Analysis
by VulDB Data Team • 06/15/2019
The vulnerability described in CVE-2006-0047 represents a critical denial of service flaw within the Freeciv 2.0 gaming server software. This issue specifically affects versions prior to 2.0.8 and demonstrates a classic buffer overflow condition that arises from improper input validation. The vulnerability exists within the packets.c module, which handles network packet processing for the multiplayer strategy game. When remote attackers send specially crafted network packets containing negative compressed size values, the server processes these malformed inputs without proper bounds checking, leading to unpredictable behavior and ultimately causing the server to crash.
The technical implementation of this vulnerability stems from inadequate validation of compressed packet sizes within the network protocol handling layer. The Freeciv server fails to properly validate the size parameter in compressed network packets, allowing negative values to propagate through the system's processing pipeline. This flaw falls under the category of improper input validation as classified by CWE-20, where the system does not adequately check the legitimacy of input data before processing. When the server attempts to allocate memory or process data structures based on these negative size values, it encounters arithmetic overflow conditions or invalid memory access patterns that result in segmentation faults or similar system crashes.
From an operational perspective, this vulnerability presents a significant risk to multiplayer gaming environments where Freeciv servers operate. Remote attackers can exploit this weakness to disrupt gaming sessions, potentially causing service outages that affect multiple players simultaneously. The impact extends beyond simple disruption as it can be used to create persistent denial of service conditions that require manual server restarts and can damage the reputation of gaming communities that rely on stable server infrastructure. The vulnerability is particularly concerning because it requires no authentication or privileged access to exploit, making it accessible to anyone capable of sending network packets to the target server.
The attack vector for this vulnerability is straightforward and network-based, requiring only that an attacker be able to send packets to the target Freeciv server on the appropriate network port. The malicious packets must contain specifically crafted negative compressed size values that trigger the flawed processing logic in packets.c. This type of attack aligns with ATT&CK technique T1498, which involves network denial of service attacks that target system resources or services. The vulnerability also demonstrates characteristics of T1595, where attackers gather information about the target system to identify exploitable conditions, and T1071, which involves application layer protocol usage for command and control communications.
Mitigation strategies for this vulnerability should focus on immediate patch deployment to update Freeciv servers to version 2.0.8 or later, which contains the necessary fixes for input validation. System administrators should implement network-level filtering to monitor and block suspicious packet patterns, particularly those with negative size indicators. Additionally, implementing proper input validation mechanisms and bounds checking within the application code can prevent similar issues from occurring in other components. The fix typically involves adding proper validation checks to ensure that compressed packet sizes are positive integers before any processing occurs, preventing the propagation of invalid data through the system's memory management and allocation routines. Regular security audits and input validation testing should be implemented to identify and address similar vulnerabilities in other network services and applications.