CVE-2018-0175: Cisco IOS, XR, and XE Software Buffer Overflow Vulnerability

CVE-2018-0175 is a vulnerability in the Link Layer Discovery Protocol (LLDP) subsystem of Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software. It can let an unauthenticated attacker on an adjacent network segment cause a denial of service or run code with elevated privileges on a vulnerable device. Network infrastructure that speaks LLDP is a high-value target; a successful attack can disrupt connectivity or give an adversary a foothold on core routing and switching gear.

Public detail is limited to the vendor and CISA descriptions. Confirm exact affected releases, fixed versions, and any configuration prerequisites directly against Cisco’s advisory before acting.

How it works

The weakness is classified as CWE-119 (improper restriction of operations within the bounds of a memory buffer). CISA describes it as a format-string issue in the LLDP subsystem. LLDP is a Layer-2 neighbor-discovery protocol commonly enabled on switch and router interfaces so devices can exchange identity and capability information.

An unauthenticated, adjacent attacker who can send crafted LLDP frames to a vulnerable interface may trigger the flaw. Depending on how the malformed input is processed, the result can be a crash (denial of service) or arbitrary code execution with elevated privileges on the device. No remote, unauthenticated attack over Layer 3 is indicated; the attacker must be able to reach the device at Layer 2 on a segment where LLDP is processed. Specific exploit mechanics and packet formats are not provided in the given facts and must not be assumed; refer to the vendor advisory for any additional technical detail.

Am I affected? How to find it in your systems

The vulnerability affects Cisco IOS, IOS XE, and IOS XR Software that include the LLDP subsystem. These images typically run on enterprise and service-provider routers, switches, and related network devices.

• Inventory every Cisco device and record the exact software train and version (show version or equivalent). Compare the list against the affected and fixed releases published in Cisco’s advisory for CVE-2018-0175.
• Determine whether LLDP is enabled globally or on individual interfaces. Devices that never process LLDP frames are at lower immediate risk, but confirm the configuration state rather than assuming defaults.
• Check management and monitoring systems for devices that advertise LLDP neighbors or that have LLDP counters incrementing.
• Review logs and telemetry for unexpected device reloads, LLDP process crashes, or anomalous Layer-2 traffic sourced from unexpected MAC addresses on ports where LLDP is active. These signs are generic indicators only; they do not prove exploitation of this CVE.

Because version ranges and platform applicability are not listed in the facts supplied here, treat every IOS/XE/XR device as potentially in scope until you have verified it against the official advisory.

How to remediate

The required action is to apply the updates Cisco released for this vulnerability, following the vendor’s installation and verification instructions. Patching is the primary and definitive fix.

• Identify the correct fixed software image for each hardware platform from the Cisco advisory.
• Schedule maintenance windows, follow change-control procedures, and verify the new image after reload (show version, confirm LLDP and routing adjacency health).
• After patching, re-enable only the LLDP features you actually need and restrict them to trusted interfaces where possible.
• Document the change and retain evidence of the pre- and post-patch versions for audit and compliance purposes.

No alternative permanent fix is described in the given facts; configuration hardening alone does not replace the vendor update.

If you can't patch immediately

Until the fixed software can be deployed, reduce exposure with compensating controls appropriate to an adjacent, unauthenticated LLDP flaw:

• Disable LLDP globally or on all interfaces that do not require it. If neighbor discovery is needed only on a subset of ports, limit LLDP to those ports and disable it elsewhere.
• Segment management and user-facing networks so that untrusted or guest devices cannot send Layer-2 frames to critical infrastructure ports.
• Apply interface-level controls (for example, storm control, port security, or ACLs that restrict unexpected ethertypes) where the platform supports them, understanding that these are partial mitigations only.
• Increase monitoring of device health (crash dumps, unexpected reloads, LLDP process state) and of Layer-2 traffic anomalies on ports that still run LLDP.
• If a network-based IPS or virtual-patching capability is available and has coverage for this CVE, enable the relevant signatures after validating they do not disrupt legitimate LLDP.

These steps lower risk but do not eliminate it; schedule the vendor update as soon as practicable.

If your data may have been exposed

Actively exploited vulnerabilities on network devices can lead to broader compromise, including traffic interception or lateral movement. Known ransomware use of this CVE is not documented in the supplied facts. If you suspect a device was targeted, isolate it, preserve logs and memory if feasible, and follow your incident-response process. As a routine hygiene step, you can run a free exposure scan of your email addresses against known breach data sets to see whether credentials or personal information have appeared in prior incidents.