CVE-2007-2525 in Linux
Summary
by MITRE
Memory leak in the PPP over Ethernet (PPPoE) socket implementation in the Linux kernel before 2.6.21-git8 allows local users to cause a denial of service (memory consumption) by creating a socket using connect, and releasing it before the PPPIOCGCHAN ioctl is initialized.
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Analysis
by VulDB Data Team • 07/20/2019
The vulnerability described in CVE-2007-2525 represents a critical memory management flaw within the Linux kernel's PPP over Ethernet implementation that specifically affects systems running kernel versions prior to 2.6.21-git8. This issue resides in the socket layer of the kernel's networking subsystem where PPPoE connections are handled, creating a condition where memory allocated for socket operations is not properly released when connections are terminated prematurely. The flaw manifests when a local user creates a PPPoE socket using the connect system call and subsequently releases the socket before the PPPIOCGCHAN ioctl command has been fully initialized, leading to a gradual accumulation of unreleased memory segments that can eventually exhaust available system resources.
The technical root cause of this vulnerability stems from improper memory deallocation within the kernel's PPPoE socket handling code path. When a socket is created and immediately released without proper initialization of the PPPIOCGCHAN ioctl operation, the kernel's memory management routines fail to reclaim all allocated memory blocks associated with that socket context. This memory leak occurs because the kernel's cleanup routines are designed to handle normal socket termination sequences but do not account for the specific edge case where a socket is destroyed before its initialization sequence is complete. The vulnerability specifically targets the kernel's socket implementation layer and operates at the kernel level, making it particularly dangerous as it can be exploited by any local user with access to the system.
The operational impact of this vulnerability extends beyond simple resource exhaustion, potentially enabling a persistent denial of service condition that can severely degrade system performance or render the system unresponsive. Local attackers can repeatedly exploit this flaw to gradually consume available memory, leading to system instability, application crashes, and ultimately complete system unavailability. The memory leak is cumulative in nature, meaning that each successful exploitation adds to the total memory consumption, and the effects compound over time until the system runs out of memory. This vulnerability is particularly concerning because it requires minimal privileges to exploit and can be automated to continuously drain system resources, making it an attractive vector for persistent attacks against Linux systems.
Mitigation strategies for this vulnerability must address both the immediate kernel-level fix and broader system hardening measures. The primary solution involves upgrading to Linux kernel version 2.6.21-git8 or later where the memory leak has been patched through proper implementation of socket cleanup routines that ensure all allocated memory is reclaimed regardless of the initialization state. System administrators should also implement monitoring solutions to detect unusual memory consumption patterns that might indicate exploitation attempts, and consider implementing resource limits on socket creation to prevent rapid exhaustion of system resources. Additionally, organizations should conduct regular security assessments of their kernel versions and maintain up-to-date patch management procedures to prevent similar vulnerabilities from being exploited in their environments. This vulnerability aligns with CWE-401, which describes improper release of memory, and represents a classic example of how kernel-level memory management flaws can be exploited for denial of service attacks, similar to patterns observed in the ATT&CK framework under the privilege escalation and resource exhaustion tactics.