CVE-2009-2903 in Linux
Summary
by MITRE
Memory leak in the appletalk subsystem in the Linux kernel 2.4.x through 2.4.37.6 and 2.6.x through 2.6.31, when the appletalk and ipddp modules are loaded but the ipddp"N" device is not found, allows remote attackers to cause a denial of service (memory consumption) via IP-DDP datagrams.
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Analysis
by VulDB Data Team • 08/22/2021
The vulnerability described in CVE-2009-2903 represents a critical memory management flaw within the Linux kernel's appletalk subsystem that affects multiple kernel versions from 2.4.x through 2.4.37.6 and 2.6.x through 2.6.31. This issue specifically manifests when the appletalk and ipddp kernel modules are loaded into memory but the corresponding ipddp"N" network device interface fails to be properly initialized or detected. The flaw stems from improper memory deallocation mechanisms within the kernel's network protocol handling code, creating a condition where allocated memory blocks are not properly released back to the system's memory pool. This memory leak occurs during the processing of IP-DDP datagrams, which are part of the AppleTalk networking protocol suite that enables communication between apple devices over tcp/ip networks.
The technical implementation of this vulnerability involves the kernel's failure to correctly handle memory allocation for network packet processing when dealing with malformed or unexpected IP-DDP datagrams. When these datagrams are received and processed by the kernel's network stack, the system allocates memory to handle the packet data structures and associated processing buffers. However, due to the flawed memory management logic, these allocated memory segments are not properly deallocated even after the packet processing is complete, leading to progressive memory consumption over time. The vulnerability specifically targets the interaction between the appletalk subsystem and the ipddp module, where the kernel assumes certain device interfaces are available but fails to properly validate the presence of these interfaces before proceeding with memory allocation. This design flaw creates a persistent memory leak that continues to accumulate until system resources are exhausted.
The operational impact of this vulnerability extends beyond simple resource consumption to create a reliable denial of service condition that can severely impact system availability and performance. Attackers can exploit this weakness by sending specially crafted IP-DDP datagrams to a target system, causing the kernel to continuously allocate memory without proper release mechanisms. As the memory leak accumulates, the system experiences progressive degradation in performance, eventually leading to complete system unresponsiveness or crashes. The vulnerability affects systems that have the appletalk and ipddp modules loaded even when these modules are not actively used, making it particularly dangerous in environments where legacy networking protocols are maintained for backward compatibility. The memory consumption pattern is particularly concerning because it occurs silently in the background without obvious system indicators, making detection and mitigation challenging for system administrators.
The root cause of this vulnerability aligns with CWE-401, which describes improper handling of memory allocation and deallocation in software systems. This weakness represents a classic memory leak scenario where allocated resources are not properly released, leading to progressive resource exhaustion. From an attack perspective, this vulnerability maps to ATT&CK technique T1499.004, which involves resource exhaustion attacks targeting memory consumption. The vulnerability also relates to T1566.001, which covers phishing attacks that could be used to deliver malicious IP-DDP packets to vulnerable systems. Effective mitigation strategies include disabling the appletalk and ipddp kernel modules when they are not actively required, implementing network-level filtering to block IP-DDP traffic, and applying kernel patches that correct the memory management logic. System administrators should also consider implementing monitoring solutions that can detect unusual memory consumption patterns and establish automated alerting mechanisms to identify potential exploitation attempts. Regular kernel updates and security patches are essential to address this vulnerability, as the flaw exists across multiple kernel versions and requires specific fixes to correct the improper memory deallocation behavior.