CVE-2008-3805 in IOS
Summary
by MITRE
Cisco IOS 12.0 through 12.4 on Cisco 10000, uBR10012 and uBR7200 series devices handles external UDP packets that are sent to 127.0.0.0/8 addresses intended for IPC communication within the device, which allows remote attackers to cause a denial of service (device or linecard reload) via crafted UDP packets, a different vulnerability than CVE-2008-3806.
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Analysis
by VulDB Data Team • 08/17/2019
The vulnerability described in CVE-2008-3805 represents a critical denial of service flaw affecting Cisco IOS versions 12.0 through 12.4 running on Cisco 10000 series, uBR10012, and uBR7200 series devices. This issue stems from improper handling of external UDP packets destined for the 127.0.0.0/8 address space, which is typically reserved for loopback communication within network devices. The flaw specifically impacts how these routers process packets that should normally be restricted to internal IPC (inter-process communication) functions, creating an unexpected pathway for external exploitation. The vulnerability operates at the network layer where the device fails to properly validate or reject incoming UDP traffic that targets the loopback address range, allowing malicious actors to craft specific packets that trigger device instability.
From a technical perspective, the vulnerability manifests when the affected Cisco IOS software processes UDP packets sent to addresses within the 127.0.0.0/8 subnet from external sources. This address range is traditionally reserved for loopback operations and should never receive external traffic, as it represents internal communication mechanisms within the device's operating system. The flaw occurs because the router's packet processing logic does not adequately distinguish between legitimate internal IPC traffic and malicious external UDP packets, leading to a condition where crafted payloads can cause the device to malfunction. The specific nature of the exploitation involves sending carefully constructed UDP packets that, when processed by the router's software, trigger an internal state machine or memory management error that results in system instability.
The operational impact of this vulnerability extends beyond simple service disruption, as it can cause complete device or linecard reloads, effectively taking the affected network infrastructure offline. This type of denial of service attack can severely impact network availability and reliability, particularly in carrier-grade environments where these devices serve as core routing infrastructure. The vulnerability affects not just individual devices but can potentially disrupt entire network segments if multiple affected routers exist within the same network topology. Network administrators may experience significant downtime while investigating and implementing mitigations, as the attack can occur remotely without requiring physical access or authentication credentials. The nature of the vulnerability also means that it can be exploited by automated tools, making it particularly dangerous in environments where network monitoring is insufficient to detect or prevent such attacks.
The technical flaw aligns with CWE-119, which addresses improper restriction of operations within a limited access scope, and can be categorized under ATT&CK technique T1499.1, which focuses on Network Denial of Service attacks. The vulnerability demonstrates poor input validation and insufficient address space restriction mechanisms within the IOS software stack. Security practitioners should implement network segmentation and access control measures to prevent external traffic from reaching these critical network devices, particularly at the boundary where external UDP traffic enters the network infrastructure. Network administrators should consider implementing ingress filtering to block traffic destined for the 127.0.0.0/8 address range from external sources, as well as monitoring for unusual patterns of UDP traffic targeting these addresses. The recommended mitigation strategy includes applying the appropriate Cisco IOS software patches, implementing proper firewall rules, and establishing network monitoring procedures to detect and alert on suspicious UDP traffic patterns that could indicate exploitation attempts.