CVE-2007-5087 in Linux
Summary
by MITRE
The ATM module in the Linux kernel before 2.4.35.3, when CLIP support is enabled, allows local users to cause a denial of service (kernel panic) by reading /proc/net/atm/arp before the CLIP module has been loaded.
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Analysis
by VulDB Data Team • 04/13/2019
The vulnerability described in CVE-2007-5087 represents a classic race condition and improper initialization issue within the Linux kernel's ATM (Asynchronous Transfer Mode) subsystem. This flaw specifically affects kernel versions prior to 2.4.35.3 and manifests when CLIP (Classical IP) support is enabled within the ATM module. The issue arises from the lack of proper synchronization and validation mechanisms during the initialization sequence of kernel modules, creating a window where subsystem components can be accessed prematurely before their dependencies are fully established.
The technical exploitation of this vulnerability occurs through a carefully timed read operation against the /proc/net/atm/arp virtual file system entry. When local users execute this specific read operation before the CLIP module has been properly loaded and initialized, the kernel's ATM subsystem fails to handle the request appropriately, leading to an immediate kernel panic. This panic results in a complete system crash and denial of service, effectively rendering the affected system unusable until manual reboot occurs. The flaw demonstrates a fundamental failure in kernel module initialization logic where the system does not properly validate whether dependent modules are available before allowing access to their interfaces.
From an operational impact perspective, this vulnerability poses significant risks to systems that rely on ATM networking capabilities, particularly in enterprise environments where kernel stability is paramount. The local nature of the exploit means that any user with access to the system can potentially trigger the denial of service condition, making it particularly dangerous in multi-user environments. The vulnerability directly violates the principle of proper resource initialization and access control that should be enforced by kernel subsystems. This flaw can be categorized under CWE-362, which addresses race conditions in kernel space operations, and aligns with ATT&CK technique T1499.004 for network denial of service attacks targeting system stability.
The mitigation strategy for this vulnerability involves applying the appropriate kernel security patches that ensure proper initialization sequence enforcement and validation of module dependencies before allowing access to virtual file system entries. System administrators should prioritize updating to kernel versions 2.4.35.3 or later where this issue has been resolved through proper synchronization mechanisms and initialization checks. Additionally, organizations should implement monitoring systems to detect anomalous access patterns to kernel virtual file systems and consider disabling unnecessary ATM support when not actively required. The fix typically involves implementing proper locking mechanisms and dependency validation checks within the kernel's ATM subsystem initialization code, ensuring that the /proc/net/atm/arp interface is only accessible when the underlying CLIP module is properly loaded and functional.