CVE-2005-1020

What it is

Secure Shell (SSH) 2 in Cisco IOS 12.0 through 12.3 allows remote attackers to cause a denial of service (device reload) (1) via a username that contains a domain name when using a TACACS+ server to authenticate, (2) when a new SSH session is in the login phase and a currently logged in user issues a send command, or (3) when IOS is logging messages and an SSH session is terminated while the server is sending data.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

1.7% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2005-05-02 04:00 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-16 22:12 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.7% in the next 30 days (EPSS).
• Severity: 7.1 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2005-05-02 04:00 UTC

Last modified

2026-06-16 22:12 UTC

Exploit probability

1.7% · EPSS, next 30 days

Weakness

CWE-287 · Improper authentication

Record status

Modified

Affected

• Cisco iOS 12.0
• Cisco iOS 12.0\(23\)s4
• Cisco iOS 12.0\(23\)s5
• Cisco iOS 12.0\(24\)s1
• Cisco iOS 12.0\(24\)s4
• Cisco iOS 12.0\(24\)s5
• Cisco iOS 12.0\(24.2\)s
• Cisco iOS 12.0\(26\)s1

Attack profile CVSS 2.0 · 7.1

Attack vector

Network

Complexity

Medium

Authentication

None

Confidentiality

None

Integrity

None

Availability

Complete

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2005-1020.md and follow it. Check whether this project is affected by CVE-2005-1020. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge