CVE-2013-6410

What it actually does

The vulnerability allows remote attackers to bypass IP-based access controls in nbd-server by using an IP address that partially matches an entry in the authfile configuration.

Why it matters to the business

Attackers may gain unauthorized access to network block devices, leading to potential data exposure or modification on storage systems without proper authentication.

How an attack unfolds

An attacker identifies a vulnerable nbd-server instance and connects using an IP address that matches only part of an allowed address in the authfile, bypassing the intended restrictions.

How to fix it

Upgrade nbd-server to version 3.5 or later. Review and harden authfile entries to enforce exact IP address matches rather than partial matches.

How to confirm the fix worked

Confirm nbd-server version is 3.5 or newer. Attempt connections with partial IP matches against known authfile entries and verify they are rejected.

Typical attack path

1. Identify exposed nbd-server instances via network scanning
2. Review or infer authfile entries to identify partial-match opportunities
3. Establish a connection to the nbd-server using a crafted partial-match IP address
4. Bypass access restrictions and read or write to block devices

How to detect it

Review nbd-server connection logs for successful authentications from IP addresses that only partially match entries in the authfile.

What your security team should do

• Upgrade all affected nbd installations to version 3.5 or later
• Audit and tighten authfile configurations across the environment
• Disable nbd services if they are not strictly required
• Implement network segmentation to limit exposure of block device services