Horizon Alert
Summary of the vulnerability and why it matters
Cisco IOS software contains a flaw that can impact the availability of network connections. This vulnerability allows an attacker to disrupt established virtual terminal connections, potentially preventing legitimate users from accessing the system through Telnet or reverse Telnet. The primary business risk involves the potential for denial of service, hindering network management and operational continuity.
- Vulnerable: Cisco IOS Telnet service
- Flaw: Refuses virtual terminal connections
- Impact: Prevents system access
Attack Path
How an attacker could exploit the issue
Attackers can exploit a vulnerability in Cisco IOS, affecting devices that allow Telnet or reverse Telnet connections. Successful exploitation may disrupt network management access for organizations. This could impact the availability of network devices and associated services, creating business risk by hindering administrative functions.
- Exposure: Unprotected Telnet ports.
- Attacker access: Network.
- Trigger: Crafted TCP connection.
- Result: Refused VTY connections.
Live Threat
Current exploitation, exposure, and threat context
This vulnerability allows remote attackers to disrupt network management services by causing connections to be refused. Such an attack could prevent legitimate administrators from accessing the system, potentially impacting operational continuity. The risk is considered medium due to the specific conditions required to exploit it.
- Attackers likely need moderate skill.
- Requires network access to Telnet ports.
- Risk is medium, impacting availability.
Priority actions
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability can allow remote attackers to cause a denial of service by refusing virtual terminal connections via crafted TCP connections to Telnet or reverse Telnet ports. The impact is a loss of remote management access to affected Cisco IOS devices. This could disrupt network operations and impact administrative access.
- Identify Cisco IOS devices with Telnet enabled.
- Restrict Telnet access or disable if not needed.
- Apply vendor updates and verify.
