CVE-2007-4537 in Skulltag
Summary
by MITRE
Heap-based buffer overflow in the Huffman decompression algorithm implemented in Skulltag 0.97d-beta4.1 and earlier allows remote attackers to execute arbitrary code via a crafted UDP packet.
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Analysis
by VulDB Data Team • 02/23/2025
The vulnerability identified as CVE-2007-4537 represents a critical heap-based buffer overflow within the Huffman decompression functionality of Skulltag version 0.97d-beta4.1 and earlier implementations. This flaw exists in the network protocol handling layer where the software processes incoming UDP packets containing compressed data. The vulnerability specifically manifests during the decompression phase of the Huffman coding algorithm, which is commonly used for data compression in network communications and multimedia applications. The heap-based nature of this overflow indicates that the vulnerable code manipulates dynamically allocated memory regions on the heap, making the exploitation particularly dangerous as it can lead to arbitrary code execution with the privileges of the affected process.
The technical implementation of this vulnerability stems from inadequate bounds checking within the Huffman decompression routine. When Skulltag receives a crafted UDP packet containing malformed compressed data, the decompression algorithm fails to validate the size of the incoming data against the allocated heap memory buffers. This allows an attacker to overflow the allocated memory space and overwrite adjacent memory regions, potentially corrupting critical data structures or executable code. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though the heap-based nature makes it more complex to exploit and detect. The specific nature of the flaw suggests that the decompression algorithm does not properly handle edge cases where compressed data exceeds expected boundaries, particularly in scenarios involving malformed Huffman trees or compressed data sequences that exceed the allocated buffer space.
The operational impact of this vulnerability is severe and directly enables remote code execution attacks against systems running vulnerable versions of Skulltag. Attackers can craft malicious UDP packets containing specially designed compressed data that triggers the buffer overflow during decompression. Successful exploitation can result in complete system compromise, allowing attackers to execute arbitrary commands with the privileges of the Skulltag process. This makes the vulnerability particularly dangerous in networked environments where Skulltag serves as a network service or game server. The attack vector requires only network access to send UDP packets, making it relatively easy to exploit in remote scenarios. The vulnerability affects not just individual systems but can potentially be leveraged to compromise entire networks if Skulltag is deployed in multi-user environments or as part of larger network infrastructure.
Mitigation strategies for CVE-2007-4537 must address both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. The primary and most effective solution involves upgrading to a patched version of Skulltag that implements proper bounds checking in the Huffman decompression algorithm. This aligns with ATT&CK technique T1203 which emphasizes the importance of patch management and software updates in preventing exploitation of known vulnerabilities. Network-level mitigations include implementing firewall rules to restrict UDP traffic to ports used by Skulltag, employing intrusion detection systems to monitor for malformed packets, and deploying network segmentation to limit the potential impact of successful exploitation. Additionally, application-level protections such as address space layout randomization, stack canaries, and heap integrity checks can provide defense-in-depth measures. Organizations should also implement regular security assessments of network services and maintain up-to-date vulnerability management processes to identify and remediate similar issues in other network protocols and applications. The vulnerability demonstrates the importance of robust input validation and memory safety practices in network protocol implementations, particularly in decompression and data processing functions that handle externally provided data.