CVE-2015-0646 in IOS
Summary
by MITRE
Memory leak in the TCP input module in Cisco IOS 12.2, 12.4, 15.0, 15.2, 15.3, and 15.4 and IOS XE 3.3.xXO, 3.5.xE, 3.6.xE, 3.8.xS through 3.10.xS before 3.10.5S, and 3.11.xS and 3.12.xS before 3.12.3S allows remote attackers to cause a denial of service (memory consumption or device reload) by sending crafted TCP packets over (1) IPv4 or (2) IPv6, aka Bug ID CSCum94811.
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Analysis
by VulDB Data Team • 12/02/2024
The vulnerability described in CVE-2015-0646 represents a critical memory leak issue within the Transmission Control Protocol input module of Cisco IOS and IOS XE operating systems. This flaw affects multiple major release versions including 12.2, 12.4, 15.0, 15.2, 15.3, and 15.4 series of IOS along with specific IOS XE versions from 3.3.x through 3.12.x series. The vulnerability specifically targets the TCP input processing functionality and manifests when the system receives specially crafted TCP packets over either IPv4 or IPv6 protocols. According to the Cisco bug ID CSCum94811, this issue enables remote attackers to exploit the memory management flaw and cause significant operational disruption to affected network devices. The vulnerability operates at the network layer where TCP packets are processed, making it particularly dangerous as it can be leveraged from remote locations without requiring local access or authentication credentials.
The technical implementation of this memory leak occurs within the TCP input module's handling of malformed or specially constructed TCP packets. When the affected Cisco IOS or IOS XE devices receive these crafted packets, the system fails to properly release allocated memory resources during the packet processing cycle. This memory allocation behavior creates a gradual accumulation of memory consumption that eventually leads to system instability. The flaw operates as a classic memory leak pattern where allocated memory blocks are not properly deallocated, causing the device's memory pool to progressively diminish over time. The vulnerability is particularly concerning because it affects the core TCP processing functionality that handles all incoming network traffic, meaning that any device running the vulnerable software is susceptible to this attack regardless of network configuration or access controls. The memory consumption pattern follows a predictable degradation curve where each crafted packet contributes to the overall memory exhaustion until the system reaches critical resource depletion levels.
The operational impact of this vulnerability extends beyond simple resource exhaustion to potentially causing complete device unavailability and service disruption. When the memory leak reaches critical thresholds, affected Cisco devices may experience spontaneous system reloads or complete failure to process additional network traffic. Network administrators may observe gradual performance degradation followed by sudden device restarts, making this vulnerability particularly dangerous in production environments where continuous network availability is critical. The remote nature of the attack means that adversaries can exploit this flaw from anywhere on the internet without requiring physical access or network credentials, making it an attractive target for malicious actors seeking to disrupt network services. This vulnerability directly impacts network infrastructure reliability and can be used to perform denial of service attacks against critical network components. The issue affects not just individual devices but entire network segments that rely on these vulnerable routers and switches for connectivity, potentially causing cascading failures across interconnected network systems.
Organizations affected by CVE-2015-0646 should prioritize immediate implementation of mitigations and patches according to the official Cisco security advisory. The primary recommended action involves applying the appropriate software updates that contain memory leak fixes for the affected IOS and IOS XE versions. Cisco released specific patches addressing this vulnerability in their software updates, and network administrators should consult the official Cisco Security Advisory for detailed patch installation instructions. Network segmentation strategies can provide temporary mitigation by limiting the exposure of vulnerable devices to external networks, though this approach does not eliminate the underlying vulnerability. Implementing TCP packet filtering rules to drop suspicious TCP packets can provide additional protection, though this method may impact legitimate network traffic. Organizations should also consider monitoring system memory usage and implementing automated alerting for unusual memory consumption patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-401, which describes improper handling of memory allocation and deallocation, and represents a clear example of how memory management flaws can be exploited for denial of service attacks. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service, demonstrating how memory leaks can be leveraged to achieve system compromise and service disruption in network infrastructure devices.