CVE-2026-87671: High Out-of-Bounds Read in Brocade Fabric OS

CVE-2026-87671 is a high severity out-of-bounds read flaw in Brocade Fabric OS, scored 7.5. 10.0.1 is the boundary in the record. Check your installed version against the affected list below, then patch or restrict access until you can. The record does not flag it as exploited.

What's affected

• Brocade Fabric OS before 10.0.1.

Severity in the record: High (7.5), vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Weakness: CWE-125.

Fix: 10.0.1 is the boundary in the record. Confirm in the advisory. The record gives the affected range only. The exact fixed builds are listed in the Broadcom advisory, which you should read before scheduling the upgrade.

How to check if you're exposed

1. Fabric OS exposes its running version from the switch command line. The firmwareshow command is the usual way to read it; confirm the command and output format against your Fabric OS release documentation.
2. Repeat on every switch, director and extension blade, since versions can differ across a fabric.
3. Compare each version with the affected range above and with the fixed builds named in the Broadcom advisory.
4. Check whether the web management interface is enabled and which networks can reach it.

Run these on every affected device, including ones in remote sites, labs and spares that are powered on.

What to do now

1. Confirm the version of every affected system using the checks above.
2. Read the vendor advisory linked in Sources and note the fixed version for your release line.
3. Schedule the update, starting with systems that face untrusted networks or hold the most sensitive data.
4. In the meantime: restrict web management access to a management network or disable it where you use the CLI only.
5. Record the change, then recheck the version to confirm it took effect.

Why it matters

The web management daemon reads URL query parameters and uses them as array indexes without range checks. That is an CWE-125 out-of-bounds read. One crafted unauthenticated HTTP request can crash the web management process and briefly disrupt management access. The record describes a denial of service, not data disclosure.

The record's KEV flag is false, so this post makes no claim that the flaw is exploited in the wild. That can change, so recheck the CISA catalog from time to time.

Network and management devices are patched less often than servers, because upgrades mean planned downtime. That gap is where a flaw like this stays open longest, so build the version check into your regular inventory.

The vector string in the record is a compact summary of how the flaw is reached and what it costs. AV is the attack vector (network, adjacent or local), PR is the privilege the attacker needs, and the C, I and A letters give the impact on confidentiality, integrity and availability. Read it against your own network layout rather than relying on the score alone.

After you patch

Patching is not the end of the job. Recheck the version on each system, because an upgrade that failed or rolled back looks the same as a success until someone looks. Keep the advisory link with your change record so the next reviewer can see why the update happened.

If you cannot patch soon, write down the reason, the compensating control you chose and a date to revisit. Exceptions without a date tend to become permanent.

Quick check

Sources

• Broadcom advisory: 39141

• Safeguard Gold: CVE-2026-87671

Last reviewed: 18 October 2026.