CVE-2017-12236 in IOS XE
Summary
by MITRE
A vulnerability in the implementation of the Locator/ID Separation Protocol (LISP) in Cisco IOS XE 3.2 through 16.5 could allow an unauthenticated, remote attacker using an x tunnel router to bypass authentication checks performed when registering an Endpoint Identifier (EID) to a Routing Locator (RLOC) in the map server/map resolver (MS/MR). The vulnerability is due to a logic error introduced via a code regression for the affected software. An attacker could exploit this vulnerability by sending specific valid map-registration requests, which will be accepted by the MS/MR even if the authentication keys do not match, to the affected software. A successful exploit could allow the attacker to inject invalid mappings of EIDs to RLOCs in the MS/MR of the affected software. This vulnerability affects Cisco devices that are configured with LISP acting as an IPv4 or IPv6 map server. This vulnerability affects Cisco IOS XE Software release trains 3.9E and Everest 16.4. Cisco Bug IDs: CSCvc18008.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/14/2021
The vulnerability described in CVE-2017-12236 represents a critical authentication bypass flaw within Cisco IOS XE software's implementation of the Locator/ID Separation Protocol. This protocol serves as a fundamental component in modern networking architectures, separating network location identifiers from routing locators to enable more flexible and scalable network operations. The affected systems include Cisco devices configured with LISP functionality acting as IPv4 or IPv6 map servers, making this vulnerability particularly concerning for enterprise networks that rely on these protocols for network segmentation and mobility management.
The technical root cause of this vulnerability stems from a logic error introduced through a code regression in the software implementation. This regression specifically impacts the authentication mechanisms that should validate map-registration requests sent to map servers and map resolvers within the LISP architecture. The flaw allows an unauthenticated remote attacker who has access to an x tunnel router to exploit the system by submitting specially crafted map-registration requests that bypass the normal authentication checks. This represents a direct violation of the security model that LISP is designed to enforce, where proper authentication is required to register Endpoint Identifiers (EIDs) with Routing Locators (RLOCs) in the map server infrastructure.
The operational impact of this vulnerability extends beyond simple unauthorized access, as successful exploitation enables attackers to inject invalid mappings of EIDs to RLOCs within the affected map server's database. This manipulation of routing information can lead to significant network disruption, including potential traffic redirection, service interruption, and unauthorized access to network resources. The attack vector specifically targets the map server/map resolver functionality, which serves as a central point for maintaining the LISP routing tables that guide network traffic between different segments. Organizations utilizing LISP for network mobility and segmentation would face particularly severe consequences, as this vulnerability undermines the fundamental security guarantees that LISP is designed to provide.
This vulnerability aligns with CWE-287, which addresses improper authentication issues in software implementations, and demonstrates characteristics consistent with ATT&CK technique T1550.001 for legitimate credentials, as it allows unauthorized actors to bypass authentication mechanisms that should prevent malicious registration of network mappings. The affected software versions span Cisco IOS XE release trains 3.9E through 16.5, indicating a prolonged period of exposure that could have allowed extensive exploitation. Organizations should immediately implement mitigation strategies including updating to patched software versions, implementing network segmentation to limit access to LISP map server functionality, and monitoring for unauthorized map registration activities. The vulnerability's classification as a remote unauthenticated attack means that network defenders must also consider perimeter security measures and access control policies to prevent exploitation from external networks.
The security implications of this vulnerability extend to broader network integrity concerns, as the ability to inject false routing information can compromise network-wide operations and potentially enable more sophisticated attacks. Network administrators should conduct comprehensive vulnerability assessments to identify all affected devices and implement appropriate controls including disabling LISP functionality when not required, implementing strict access controls on map server components, and establishing robust monitoring for anomalous map registration patterns. This vulnerability underscores the critical importance of maintaining proper authentication mechanisms in network infrastructure protocols and demonstrates how code regressions can introduce security weaknesses that may persist for extended periods without detection.