Cisco IMC Vulnerability Allows Attackers to Gain Elevated Privileges

Cisco has issued a security advisory regarding a critical privilege escalation vulnerability (CVE-2025-20261) affecting its Integrated Management Controller (IMC) software used in UCS B-Series, C-Series, S-Series, and X-Series servers.

The flaw, rated with a CVSS base score of 8.8, could allow an authenticated, remote attacker to gain elevated privileges and unauthorized access to internal services via SSH, potentially leading to full system compromise.

The vulnerability stems from insufficient restrictions on access to internal services within the IMC’s SSH connection handling.

An attacker with a valid user account can exploit the flaw by using crafted syntax during SSH connections, enabling them to perform unauthorized modifications, including the creation of new administrator accounts.

Affected Products and Exploitation Details

The vulnerability impacts a wide range of Cisco products if they are running a vulnerable software release and accept incoming SSH connections to the IMC.

Notably, UCS C-Series and S-Series servers in standalone mode accept SSH connections by default. For B-Series and X-Series servers, SSH access is enabled only if a Serial over LAN (SoL) policy is active.

Vulnerable Product Families:

• UCS B-Series Blade Servers
• UCS C-Series Rack Servers
• UCS S-Series Storage Servers
• UCS X-Series Modular System

Additional Cisco Appliances at Risk:

• Application Policy Infrastructure Controller (APIC)
• Business Edition 6000/7000 Appliances
• Catalyst Center Appliances (formerly DNA Center)
• Cloud Services Platform (CSP) 5000 Series
• HyperFlex Nodes and Edge Nodes
• Secure Firewall Management Center Appliances
• Secure Network Analytics Appliances
• And many more

Technical Details and Exploit Scenario:

• The vulnerability is classified under CWE-923 (Improper Restriction of Communication Channel to Intended Endpoints).
• Attackers require an authenticated user account (privileges as low as read-only) to exploit the flaw.
• By connecting to the IMC via SSH with specially crafted commands, attackers can bypass normal privilege restrictions.

CVSS Vector:CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

This vector indicates a network-based attack with low complexity, requiring low privileges and no user interaction, with high impact on confidentiality, integrity, and availability1.

Mitigation, Remediation, and Fixed Releases

Cisco has released free software updates to address the vulnerability. There are no workarounds, but mitigation is possible by disabling SSH access to the IMC if not required.

For standalone UCS C-Series and S-Series servers, SSH can be disabled via the IMC web UI. For managed environments, disabling the Serial over LAN policy will prevent SSH access.

Fixed Software Versions:

Product Family / Mode	First Fixed Release
UCS B-Series/X-Series (UCS Manager)	4.1(3n), 4.2(3k), 4.3(4c)
UCS B-Series (Intersight Managed)	4.2(3i), 5.2(2.240073)
UCS X-Series (Intersight Managed)	5.0(4f), 5.2(2.240073)
UCS C/S-Series (Standalone/Intersight)	4.2(2f), 4.2(3b)
UCS C/S-Series (UCS Manager)	4.2(2c), 4.2(3b)

Administrators are urged to upgrade to the fixed releases listed above.

For certain appliances, specific firmware or hotfixes must be applied as detailed in Cisco’s advisory.

This vulnerability highlights the importance of timely patch management and the risks posed by improper access controls in critical infrastructure components.

While no public exploitation has been reported as of June 2025, Cisco recommends immediate action to mitigate potential threats and ensure the security of affected systems.

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