Cisco has disclosed a critical security vulnerability affecting its Integrated Management Controller (IMC) across multiple UCS server series that could enable authenticated attackers to gain elevated privileges and potentially create unauthorized administrator accounts.
The vulnerability, identified in SSH connection handling mechanisms, poses significant risks to enterprise infrastructure security and requires immediate attention from system administrators.
The vulnerability stems from insufficient restrictions on access to internal services within Cisco’s IMC systems.
Attackers with valid user credentials can exploit this weakness by employing crafted syntax when establishing SSH connections to affected Cisco IMC devices.
Once successfully exploited, the vulnerability grants attackers access to internal services with elevated privileges, potentially allowing unauthorized system modifications and the creation of new administrator accounts.
The affected systems include UCS B-Series Blade Servers, UCS C-Series Rack Servers, UCS S-Series Storage Servers, and UCS X-Series Modular Systems, provided they are running vulnerable software releases and accept incoming SSH connections.
Notably, Cisco UCS C-Series and UCS S-Series Servers in standalone mode accept SSH connections by default, while other series require Serial over LAN (SoL) policy enablement.
IMC Vulnerability
The vulnerability’s impact extends beyond core UCS servers to numerous Cisco appliances built on preconfigured UCS C-Series platforms.
Affected products include Application Policy Infrastructure Controller (APIC) Servers, Catalyst Center Appliances, HyperFlex Nodes, Nexus Dashboard Appliances, and Secure Firewall Management Center Appliances, among others.
This broad scope significantly amplifies the potential impact across enterprise environments utilizing Cisco’s unified computing infrastructure.
Cisco has confirmed that specific products remain unaffected, including 5000 Series Enterprise Network Compute Systems (ENCS), Catalyst 8300 Series Edge uCPE, and UCS E-Series Servers.
The vulnerability was discovered during internal security testing, and Cisco’s Product Security Incident Response Team reports no current awareness of public exploitation or malicious use.
Mitigations
Cisco has released comprehensive software updates addressing the vulnerability across all affected product lines.
For UCS B-Series and X-Series servers in UCS Manager mode, fixed releases include versions 4.1(3n), 4.2(3k), and 4.3(4c).
UCS C-Series and S-Series servers require updates to versions 4.2(2f), 4.2(3b), or migration to version 4.3, which is not vulnerable.
Organizations unable to immediately implement software updates can deploy mitigation strategies by disabling SSH access to Cisco IMC where not operationally required.
For standalone UCS C-Series and S-Series servers, administrators can disable SSH through the Communication Services menu, while managed servers require disabling Serial over LAN policies.
Cisco emphasizes that no workarounds exist for this vulnerability, making either software updates or SSH access disabling the only viable protection methods.
Customers should evaluate mitigation effectiveness in their specific environments, as implementation may impact network functionality or performance based on deployment scenarios.
The company provides free security updates through standard channels for customers with valid service contracts and licensing agreements.
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