CVE-2021-3716

What it is

A flaw was found in nbdkit due to to improperly caching plaintext state across the STARTTLS encryption boundary. A MitM attacker could use this flaw to inject a plaintext NBD_OPT_STRUCTURED_REPLY before proxying everything else a client sends to the server, potentially leading the client to terminate the NBD session. The highest threat from this vulnerability is to system availability.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. Limited direct impact.

Exploit odds

0.6% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2022-03-02 23:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:05 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.6% in the next 30 days (EPSS).
• Severity: 3.1 LOW (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2022-03-02 23:15 UTC

Last modified

2026-06-17 04:05 UTC

Exploit probability

0.6% · EPSS, next 30 days

Weakness

CWE-924

Record status

Modified

Affected

• Nbdkit Project Nbdkit < 1.24.6
• Nbdkit Project Nbdkit < 1.26.5
• Nbdkit Project Nbdkit < 1.27.6
• Redhat Enterprise Linux 8.0

Attack profile CVSS 3.1 · 3.1

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-3716.md and follow it. Check whether this project is affected by CVE-2021-3716. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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