CVE-2007-4643 in Doomsday
Summary
by MITRE
Integer underflow in Doomsday (aka deng) 1.9.0-beta5.1 and earlier allows remote attackers to cause a denial of service (daemon crash) via a PKT_CHAT packet with a data length less than 3, which triggers an erroneous malloc, possibly related to the Sv_HandlePacket function in sv_main.c.
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Analysis
by VulDB Data Team • 08/05/2019
The vulnerability identified as CVE-2007-4643 represents a critical integer underflow condition within the Doomsday engine version 1.9.0-beta5.1 and earlier releases. This flaw manifests specifically within the network packet handling mechanism of the daemon process, where the application fails to properly validate packet data lengths before processing them. The issue occurs when a malicious actor sends a PKT_CHAT packet containing data that is less than three bytes in length, creating a scenario where integer arithmetic results in an unexpectedly small value that subsequently triggers improper memory allocation behavior.
The technical implementation of this vulnerability resides in the Sv_HandlePacket function located within the sv_main.c source file, which serves as the primary packet processing handler for the server daemon. When the application encounters a packet with insufficient data length, the integer underflow causes the malloc function to attempt allocating a negative or extremely small amount of memory, leading to memory corruption and ultimately causing the daemon process to crash. This represents a classic example of improper input validation and memory management handling that violates fundamental security principles.
From an operational impact perspective, this vulnerability enables remote attackers to execute a reliable denial of service attack against Doomsday engine servers without requiring any authentication or privileged access. The daemon crash resulting from this condition effectively renders the affected service unavailable to legitimate users, disrupting gameplay and potentially causing significant disruption to multiplayer gaming environments that depend on these servers. The vulnerability's remote exploitability means that attackers can trigger the condition from any network location, making it particularly dangerous in publicly accessible gaming environments.
The underlying cause of this vulnerability aligns with CWE-191, which specifically addresses integer underflow conditions where a calculation results in a value that is smaller than the minimum representable value for the data type. This flaw also corresponds to ATT&CK technique T1499.004, which covers network denial of service attacks through exploitation of software vulnerabilities. The vulnerability demonstrates poor defensive programming practices where boundary checks are insufficient to prevent arithmetic operations from producing invalid memory allocation requests, highlighting the need for robust input validation and proper integer overflow/underflow protection mechanisms.
Mitigation strategies should focus on implementing proper input validation before any arithmetic operations occur, ensuring that packet data lengths are verified against minimum acceptable values before processing. The fix should involve adding explicit checks to validate that packet data lengths meet minimum requirements, typically requiring at least three bytes for proper packet parsing. Additionally, memory allocation functions should include bounds checking to prevent allocation of invalid memory sizes, and the application should implement proper error handling that gracefully manages malformed packets rather than allowing them to cause crashes. Regular security updates and code reviews focusing on integer arithmetic operations and memory management practices are essential to prevent similar vulnerabilities from emerging in future releases.