CVE-2025-1976

What is Broadcom Brocade Fabric OS?

Brocade Fabric OS (FOS) is the operating system running on Brocade Fibre Channel SAN (Storage Area Network) switches — enterprise hardware that connects servers to shared storage arrays. Broadcom acquired Brocade in 2017 and continues to sell and support the Brocade SAN switch product line under the Broadcom brand.

SAN switches are critical infrastructure components in data centers: they form the fabric over which servers communicate with storage. A compromised SAN switch gives an attacker read/write access to all storage traffic passing through it — including access to database volumes, backup repositories, and virtual machine disk images. This makes SAN switches extremely high-value targets for threat actors seeking data exfiltration or ransomware deployment.

Overview

Broadcom Brocade Fabric OS contains a code injection vulnerability (CWE-94) that allows a local user with administrative privileges to execute arbitrary code with full root privileges. An attacker who has already gained admin-level access to a Brocade SAN switch's management interface can exploit this vulnerability to escape the CLI sandbox and execute arbitrary commands at the OS root level, gaining unrestricted control of the device.

CISA added this to the KEV catalog just four days after publication, reflecting the severity of in-the-wild exploitation of SAN infrastructure.

Affected Versions

Refer to Broadcom Security Advisory 25602 for the complete list of affected versions and corresponding fixed releases.

Technical Details

Brocade Fabric OS provides a specialized CLI for managing SAN switch configuration. Administrative users can log in via SSH and interact with FOS commands. The vulnerability is in the command processing layer: certain inputs can inject code that is executed outside the expected CLI sandbox, with the result running at full root privilege.

Attack characteristics:

• Attack vector: Local — requires authenticated access to the FOS management interface (SSH/console)
• High privileges required: Must already have administrative access to the FOS CLI
• No user interaction: Exploitation is direct once access is obtained
• Full impact: Confidentiality, Integrity, and Availability all rated High — arbitrary code execution at root means complete device control

Why admin-to-root matters on SAN switches: Even "administrative" FOS CLI access is normally sandboxed — admins can manage switch fabric configurations but cannot access the underlying Linux OS or modify system-level files. Root access bypasses this sandbox, enabling:

• Installation of persistent firmware-level implants
• Direct access to storage I/O at the hardware level
• Modification of zoning configurations to redirect storage traffic
• Exfiltration of SAN switch credentials and fabric topology data
• Disabling of storage access controls (LUN masking) to reach storage volumes directly

In ransomware operations, root access to a SAN switch can allow attackers to identify and target backup storage repositories, deleting or encrypting backup volumes before deploying ransomware on production systems.

Discovery

Broadcom attributed the vulnerability in its April 2025 security advisory. The rapid CISA KEV addition (4 days post-publication) indicates the vulnerability was already being actively exploited at the time of disclosure.

Exploitation Context

CISA added CVE-2025-1976 to the KEV catalog on April 28, 2025 — four days after Broadcom's advisory — confirming active exploitation targeting SAN infrastructure. Brocade SAN switches are pervasive in enterprise and service provider data centers, and their management interfaces are sometimes accessible from privileged network segments that are less rigorously monitored than perimeter-facing systems.

Threat actors compromising storage infrastructure represent a significant ransomware pre-positioning risk: access to backup storage volumes allows attackers to destroy or encrypt backup data before detonating ransomware on production systems, eliminating recovery options.

Remediation

1. Apply the patched Fabric OS version — upgrade per the Broadcom Security Advisory 25602 for your specific FOS version branch.
2. Restrict SAN management network access — ensure FOS management interfaces (SSH, serial console) are accessible only from a dedicated, monitored management VLAN, not from general server networks.
3. Audit FOS administrative accounts — review all accounts with admin-level FOS CLI access; remove or rotate credentials for accounts that may have been compromised.
4. Review zoning and LUN masking configurations — check for unauthorized changes to fabric zoning or LUN masking that could indicate post-exploitation tampering.
5. Enable FOS security logging — ensure Brocade switch audit logs are forwarded to a central SIEM for anomaly detection.
6. Inventory internet-facing management interfaces — confirm FOS management ports are not directly reachable from the internet or untrusted networks.