Cisco UCS Central Vulnerable to Authenticated RCE (CVE-2026-76506)
Cisco Patches High-Severity RCE Flaw in UCS Central Software
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Executive Summary
On November 4, 2026, Cisco disclosed a high-severity vulnerability, CVE-2026-76506, affecting its Cisco UCS Central Software. The flaw resides in the web-based management interface and stems from insufficient input validation. A remote attacker with valid user credentials—even those with low privileges—could exploit this vulnerability by sending a specially crafted HTTP request. Successful exploitation could lead to remote code execution (RCE) on the underlying operating system, arbitrary file writes, and information disclosure. Cisco has released software updates to address the issue and confirms there are no workarounds. At the time of disclosure, there was no evidence of active exploitation.
Vulnerability Details
- CVE ID: CVE-2026-76506
- CVSS 3.1 Score: 7.6 (High)
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
The vulnerability is caused by improper validation of user-supplied input within an HTTP request sent to the web-based management interface of the UCS Central Software. An attacker can leverage this by crafting a malicious HTTP request to a vulnerable endpoint. The key prerequisite is that the attacker must be authenticated to the system. This makes the vulnerability particularly dangerous in scenarios involving insider threats or when an attacker has already obtained low-privileged user credentials through other means, such as phishing or password spraying.
A successful exploit could grant the attacker the ability to execute arbitrary commands on the appliance, effectively leading to a full system compromise.
Affected Systems
The vulnerability affects the following Cisco product:
- Cisco UCS Central Software: All releases prior to 2.1(2c).
Cisco has confirmed that the vulnerability impacts the product regardless of its specific configuration. Systems running version 2.0 or earlier are not eligible for a direct patch and must be migrated to a supported, fixed version.
Exploitation Status
As of the disclosure date (November 4, 2026), the Cisco Product Security Incident Response Team (PSIRT) was not aware of any public announcements or malicious use of this vulnerability in the wild. However, given the nature of the flaw, the release of a technical proof-of-concept (PoC) is plausible, which would significantly increase the risk of exploitation.
Impact Assessment
An attacker who successfully exploits CVE-2026-76506 could gain significant control over a critical piece of data center management infrastructure. Cisco UCS Central is used to manage multiple Cisco UCS domains, which are foundational components of modern data centers and private cloud environments. Compromising the central management appliance could allow an attacker to:
- Gain access to sensitive management-plane data.
- Execute arbitrary code on the appliance, potentially with root privileges.
- Pivot from the UCS Central appliance to the managed UCS domains, enabling widespread lateral movement across the virtualized infrastructure.
- Disrupt data center operations by modifying configurations or shutting down servers.
The requirement for authentication lowers the immediate risk from unauthenticated external attackers but poses a severe threat from insiders or in post-compromise scenarios.
Cyber Observables — Hunting Hints
The following patterns may help identify vulnerable systems or exploitation attempts:
sh, bash, python, or perl being executed by the web service account./var/log/httpd/Detection Methods
- Vulnerability Scanning: Use authenticated vulnerability scans to identify instances of Cisco UCS Central Software running a vulnerable version.
- Log Analysis: Ingest web access logs from the UCS Central management interface into a SIEM. Create rules to alert on an unusual volume of requests, requests with abnormal parameters, or successful logins followed by suspicious activity from non-administrative IP ranges. This corresponds to D3FEND's
Web Session Activity Analysis. - Endpoint Monitoring: If possible, monitor the UCS Central appliance for anomalous process execution, file creation in unusual directories, or unexpected outbound network connections originating from the appliance itself.
Remediation Steps
Cisco has released software updates to address this vulnerability. There are no workarounds.
- Primary Action: Patching: Administrators should upgrade their Cisco UCS Central Software deployments to version 2.1(2c) or later. The patch can be downloaded from the official Cisco Software Center.
- Migration for Older Versions: For systems running version 2.0 or earlier, a direct patch is not available. These systems must be migrated to a fixed release (2.1(2c) or newer).
- Compensating Controls: Before patching can be completed, organizations should strictly enforce access controls to the UCS Central management interface. Restrict access to a dedicated, isolated management network and a limited set of trusted administrative IP addresses. This is an application of D3FEND's
Network Isolation. - Verify Update: After applying the update, administrators should verify that the new version is running and that all services are functioning correctly.
Timeline of Events
MITRE ATT&CK Mitigations
Update Software
Applying the security patches provided by Cisco is the only way to fully remediate this vulnerability.
Restricting network access to the UCS Central management interface to only trusted administrative hosts significantly reduces the attack surface.
Privileged Account Management
Enforcing strong password policies and regularly auditing privileged accounts can help prevent the initial credential compromise required to exploit this flaw.
D3FEND Defensive Countermeasures
The primary and most critical action is to apply the patch from Cisco immediately. Organizations should prioritize updating their Cisco UCS Central Software to version 2.1(2c) or newer. Given that this vulnerability allows for remote code execution on a central data center management tool, the risk is substantial. A systematic patch management program should identify all instances of UCS Central, schedule an urgent maintenance window, and deploy the update. For systems on unsupported versions like 2.0, a migration project to a supported release must be initiated. Verifying the update's success by checking the software version post-installation is a crucial final step.
As a critical compensating control, the management interface of the Cisco UCS Central appliance must be isolated from general corporate and user networks. It should reside on a dedicated, out-of-band management network. Firewall rules should be configured to strictly limit access to this interface, allowing connections only from a small, well-defined set of administrator jump boxes or bastion hosts. All other inbound traffic should be denied by default. This measure drastically reduces the attack surface by preventing any user with compromised credentials on the general network from even reaching the vulnerable login page, thereby thwarting exploitation attempts.
Timeline of Events
Cisco discloses vulnerability CVE-2026-76506 and releases software updates.
Sources & References
Article Author
Jason Gomes
• Cybersecurity PractitionerCybersecurity professional with over 10 years of specialized experience in security operations, threat intelligence, incident response, and security automation. Expertise spans SOAR/XSOAR orchestration, threat intelligence platforms, SIEM/UEBA analytics, and building cyber fusion centers. Background includes technical enablement, solution architecture for enterprise and government clients, and implementing security automation workflows across IR, TIP, and SOC use cases.
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