CVE-2018-0180

What is Cisco IOS Login Enhancements (Login Block)?

Login Enhancements, or Login Block, is a Cisco IOS feature that watches for patterns consistent with dictionary or brute-force login attempts against device management access and temporarily blocks further attempts from the offending source. CVE-2018-0180 is a second, distinct vulnerability in this same feature, published in the same advisory as the nearly identical CVE-2018-0179.

Overview

CVE-2018-0180 is a medium-severity denial-of-service vulnerability in the Login Block feature of Cisco IOS Software. An unauthenticated, remote attacker can send a sequence of crafted login attempts that triggers a fault in the Login Block processing logic, forcing the affected device to reload.

Technical Details

The vulnerability is classified under CWE-399 (resource management errors). As with its sibling CVE, the flaw lies in how Login Block processes incoming, pre-authentication login attempt data — meaning an attacker can trigger it purely through unauthenticated interaction with the login prompt or management service, without ever needing valid credentials.

Discovery

Cisco identified and fixed this issue internally, publishing it in the same March 2018 semiannual IOS security advisory as the closely related CVE-2018-0179.

Exploitation Context

CISA's KEV catalog listing confirms this vulnerability has been exploited in real-world attacks. As with CVE-2018-0179, this offers attackers a way to disrupt a device via its own brute-force protection mechanism, and organizations exposed to one of the pair should assume exposure to both since they share a root cause category, disclosure date, and fixed release.

Remediation

1. Identify Cisco IOS devices with Login Block/Login Enhancements configured and confirm their current software version.
2. Apply the Cisco-published fixed software release, which addresses this vulnerability together with CVE-2018-0179.
3. Restrict management-plane access (SSH, Telnet, HTTP/HTTPS) to trusted administrative networks.
4. Monitor for unexpected device reloads correlated with login attempt activity.
5. Verify that patching efforts for CVE-2018-0179 also covered this CVE, since both were fixed in the same software release.