CVE-2018-0117 in VPC-DI
Summary
by MITRE
A vulnerability in the ingress packet processing functionality of the Cisco Virtualized Packet Core-Distributed Instance (VPC-DI) Software could allow an unauthenticated, remote attacker to cause both control function (CF) instances on an affected system to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient handling of user-supplied data by the affected software. An attacker could exploit this vulnerability by sending malicious traffic to the internal distributed instance (DI) network address on an affected system. A successful exploit could allow the attacker to cause an unhandled error condition on the affected system, which would cause the CF instances to reload and consequently cause the entire VPC to reload, resulting in the disconnection of all subscribers and a DoS condition on the affected system. This vulnerability affects Cisco Virtualized Packet Core-Distributed Instance (VPC-DI) Software N4.0 through N5.5 with the Cisco StarOS operating system 19.2 through 21.3. Cisco Bug IDs: CSCve17656.
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Analysis
by VulDB Data Team • 02/02/2021
The vulnerability identified as CVE-2018-0117 resides within the Cisco Virtualized Packet Core-Distributed Instance (VPC-DI) software, specifically impacting the ingress packet processing functionality that governs how incoming network traffic is handled within the system. This flaw represents a critical weakness in the software's ability to properly validate and process user-supplied data, creating an exploitable condition that can be leveraged by remote attackers without requiring authentication credentials. The affected software versions span from N4.0 through N5.5, operating on Cisco StarOS versions 19.2 through 21.3, making a substantial portion of the VPC-DI deployment landscape vulnerable to this specific threat vector.
The technical implementation of this vulnerability stems from inadequate input validation mechanisms within the control function (CF) instances of the VPC-DI software. When maliciously crafted packets are transmitted to the internal distributed instance network address, the system fails to properly sanitize or handle the malformed data, leading to an unhandled error condition that triggers system instability. This improper data handling directly correlates to CWE-20, which describes inadequate input validation as a fundamental weakness in software security design. The vulnerability's exploitation pathway demonstrates a classic remote code execution vector through malformed packet processing, where the attacker's crafted traffic bypasses normal security controls and directly targets the software's parsing logic.
The operational impact of this vulnerability extends far beyond simple service disruption, as successful exploitation results in complete system reloads that cascade through the entire VPC infrastructure. When the CF instances reload, they trigger a full system restart that disconnects all subscribers and renders the network service unavailable to users. This denial of service condition affects not just individual network functions but the entire distributed instance architecture, creating widespread service degradation that can impact thousands of users simultaneously. The vulnerability's potential for causing complete system outages places it within the ATT&CK framework's privilege escalation and denial of service tactics, where the attacker can leverage a single exploit to achieve maximum disruption with minimal effort.
Mitigation strategies for CVE-2018-0117 require immediate implementation of network segmentation and access control measures to prevent unauthorized access to the internal DI network addresses. Organizations should deploy ingress filtering and packet validation mechanisms to identify and drop malformed traffic before it reaches the vulnerable CF instances. The most effective remediation involves applying the official Cisco software patches that address the input validation deficiencies in the affected VPC-DI software versions. Additionally, implementing network monitoring solutions that can detect unusual reload patterns and traffic spikes to internal network addresses will help identify exploitation attempts. Security teams should also consider temporary network isolation of VPC-DI components until proper patches are deployed, as recommended in the Cisco Security Advisory associated with CSCve17656, which provides specific guidance on mitigating this vulnerability through configuration changes and software updates.