CVE-2011-10020 in Server
Summary
by MITRE • 08/20/2025
Kaillera Server version 0.86 is vulnerable to a denial-of-service condition triggered by sending a malformed UDP packet after the initial handshake. Once a client sends a valid HELLO0.83 packet and receives a response, any subsequent malformed packet causes the server to crash and become unresponsive. This flaw stems from improper input validation in the server’s UDP packet handler, allowing unauthenticated remote attackers to disrupt service availability.
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Analysis
by VulDB Data Team • 08/20/2025
The vulnerability identified as CVE-2011-10020 affects Kaillera Server version 0.86 and represents a significant denial-of-service weakness that undermines system availability. This flaw operates within the context of networked gaming services where multiple clients connect to a central server to participate in multiplayer sessions. The vulnerability specifically targets the server's UDP packet handling mechanism, which is fundamental to maintaining real-time communication between clients and the gaming infrastructure. The attack vector is particularly concerning because it requires minimal privileges and can be executed remotely without authentication, making it accessible to any attacker with network access to the vulnerable server.
The technical root cause of this vulnerability lies in inadequate input validation within the server's UDP packet processing code. When a client successfully establishes initial communication by sending a valid HELLO0.83 packet, the server responds appropriately and enters a state where it expects subsequent legitimate packets. However, the server's packet handler fails to properly validate incoming data structures, particularly when processing malformed UDP packets that deviate from expected protocols. This weakness creates a condition where any incorrectly formatted packet can trigger an unhandled exception or memory corruption, leading to immediate server termination. The vulnerability manifests as a complete service disruption where the server becomes unresponsive and must be manually restarted to restore functionality.
The operational impact of this vulnerability extends beyond simple service interruption to encompass broader security implications for gaming infrastructure and network availability. Since the attack can be executed by unauthenticated remote actors, it represents a significant threat to gaming services that rely on Kaillera Server implementations. Network administrators and system operators face the challenge of maintaining uptime for gaming services while dealing with this vulnerability, as the attack can be launched repeatedly and systematically degrades service quality. The vulnerability's exploitation does not require sophisticated techniques or privileged access, making it particularly dangerous for public gaming servers where multiple users may be connected simultaneously.
Mitigation strategies for CVE-2011-10020 should focus on immediate patching of the vulnerable software version, as well as implementing network-level protections to reduce exposure. The most effective solution involves upgrading to a patched version of Kaillera Server that properly validates all incoming UDP packets before processing them. Network administrators should also consider implementing firewall rules that limit UDP packet processing to known legitimate sources or applying rate-limiting mechanisms to reduce the impact of potential attacks. Additionally, monitoring systems should be enhanced to detect unusual packet patterns that may indicate exploitation attempts. This vulnerability aligns with CWE-129, which addresses improper input validation, and demonstrates characteristics consistent with attack patterns found in the MITRE ATT&CK framework under the service stoppage and denial-of-service categories, emphasizing the importance of robust input validation and proper error handling in network services.