CVE-2006-1999 in OpenTTD
Summary
by MITRE
The multiplayer menu in OpenTTD 0.4.7 allows remote attackers to cause a denial of service via a UDP packet with an incorrect size, which causes the client to return to the main menu.
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Analysis
by VulDB Data Team • 04/08/2025
The vulnerability described in CVE-2006-1999 represents a classic denial of service flaw within the multiplayer networking implementation of OpenTTD version 0.4.7. This issue specifically targets the game's multiplayer menu system which handles UDP packet communication between clients and servers. The flaw manifests when a remote attacker sends a UDP packet with an incorrect size to a connected OpenTTD client, causing the application to abruptly terminate the multiplayer session and return the user to the main menu interface. This behavior constitutes a denial of service condition as legitimate users are unable to maintain their multiplayer gaming sessions.
The technical implementation of this vulnerability stems from inadequate input validation within the UDP packet processing code of the multiplayer menu component. When the client receives a malformed UDP packet with an unexpected size, the parsing routine fails to properly handle the malformed data structure, leading to an unhandled exception or abrupt program termination. This type of vulnerability falls under CWE-129, which addresses improper validation of input boundaries, and CWE-248, which covers exposure of unintended executable code. The lack of proper bounds checking and error handling in the network packet parsing routine creates an exploitable condition where malformed data can trigger system instability.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by malicious actors to repeatedly interrupt multiplayer gaming sessions, potentially affecting server performance and user experience. In multiplayer gaming environments, this vulnerability becomes particularly dangerous as it can be used to disrupt ongoing games, forcing players to reconnect and potentially lose game progress. The vulnerability affects the availability aspect of the system by preventing legitimate users from accessing the multiplayer functionality, which is a core feature of OpenTTD's appeal. Network-based attacks exploiting this flaw can be executed with minimal resources, making it an attractive vector for denial of service attacks against gaming servers.
Mitigation strategies for this vulnerability should focus on implementing robust input validation and error handling within the network packet processing components. The recommended approach involves adding comprehensive bounds checking for all incoming UDP packets, implementing proper exception handling to gracefully manage malformed data, and ensuring that the multiplayer menu system can recover from malformed packet inputs without terminating the application. Additionally, network-level filtering can be implemented to drop packets with suspicious sizes or malformed headers. Organizations should also consider implementing rate limiting to prevent rapid successive attacks and ensure that the system maintains proper state management during network communication. This vulnerability highlights the importance of defensive programming practices and proper error handling in networked applications, aligning with ATT&CK technique T1498 which covers network denial of service attacks and T1595 which addresses network infiltration through malformed data payloads.