CVE-2014-2183 in IOS XE
Summary
by MITRE
The L2TP module in Cisco IOS XE 3.10S(.2) and earlier on ASR 1000 routers allows remote authenticated users to cause a denial of service (ESP card reload) via a malformed L2TP packet, aka Bug ID CSCun09973.
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Analysis
by VulDB Data Team • 05/12/2026
The vulnerability identified as CVE-2014-2183 represents a critical denial of service weakness within the Layer 2 Tunneling Protocol implementation of Cisco IOS XE software running on ASR 1000 series routers. This flaw specifically affects versions 3.10S(.2) and earlier, creating a scenario where authenticated remote attackers can exploit malformed L2TP packets to force the reload of ESP (Encryption Service Processor) cards. The vulnerability operates at the network protocol level, targeting the fundamental packet processing mechanisms that handle L2TP tunnel establishment and maintenance. The affected ASR 1000 routers are widely deployed in enterprise and service provider networks, making this issue particularly concerning from a operational security perspective. The bug ID CSCun09973 specifically documents this weakness in Cisco's internal tracking system, indicating it was recognized and classified as a significant security concern requiring immediate attention.
The technical exploitation of this vulnerability occurs through careful crafting of L2TP packets that contain malformed data structures or invalid field values within the protocol headers. When the affected IOS XE software processes these malformed packets, it fails to properly validate the incoming data, leading to an unexpected system state that triggers the automatic reload of the ESP card components. This reload process essentially restarts the encryption services on the router, disrupting ongoing network communications and potentially causing temporary network outages. The vulnerability stems from insufficient input validation within the L2TP module's packet parsing routines, where the software does not adequately sanitize or reject malformed data before attempting to process it. This type of flaw typically falls under CWE-129, which covers improper validation of input boundaries, and represents a classic example of a buffer over-read or improper input handling vulnerability that can be exploited to cause system instability.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader network reliability and availability concerns. When ESP cards reload, they temporarily remove encryption capabilities from the router, potentially exposing network traffic to interception or modification attacks during the brief outage period. Network administrators may experience unexpected service interruptions that could affect critical business operations, particularly in environments where the ASR 1000 routers serve as primary network infrastructure components. The authenticated nature of the attack means that an attacker must have valid credentials to exploit the vulnerability, but this requirement does not significantly reduce the threat level since compromised accounts or legitimate administrative access could be leveraged. From an attacker's perspective, this vulnerability provides a straightforward method for causing disruption while maintaining relative anonymity, as the attack requires only basic network access and authentication credentials.
Mitigation strategies for CVE-2014-2183 should focus on immediate software updates and network segmentation approaches to limit the attack surface. Cisco released patches and software updates specifically addressing this vulnerability, which should be deployed as soon as possible across all affected ASR 1000 routers in the network infrastructure. Network administrators should also consider implementing access controls to limit authentication access to the router management interfaces and establish monitoring systems to detect unusual ESP card reload patterns. The implementation of network access control lists and firewall rules can help restrict L2TP traffic to only trusted sources, reducing the potential attack vectors. Additionally, organizations should conduct regular vulnerability assessments to identify other potential weaknesses in their network infrastructure and establish incident response procedures that include specific protocols for handling ESP card reload events. The vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a clear example of how protocol-level vulnerabilities can be exploited to compromise network availability and operational continuity.