---
id: CVE-2026-19538
title: >-
  The BLOCKED access control list items that are evaluated to deny access on the
  the proxy protocol port can be bypassed completely when connecting over TCP or
  TLS and sending the query twice on connection that is kept open.
summary: >-
  The BLOCKED access control list items that are evaluated to deny access on the
  the proxy protocol port can be bypassed completely when connecting over TCP or
  TLS and sending the query twice on connection that is kept open.
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-290
  - CWE-672
vendor: nlnetlabs
product: nsd
affected:
  - 'nsd >= 4.8.0, < 4.15.1'
patched:
  - nsd 4.15.1
published: '2026-08-26'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T19:59:34.000'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-19538'
references:
  - url: 'https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-19538.txt'
    label: sep@nlnetlabs.nl
tags:
  - nvd
epss: 0.00233
epssPercentile: 0.12644
ingestedAt: '2026-09-08T20:10:03.158Z'
---

## Overview

The BLOCKED access control list items that are evaluated to deny access on the the proxy protocol port can be bypassed completely when connecting over TCP or TLS and sending the query twice on connection that is kept open.

## Affected

- `nsd >= 4.8.0, < 4.15.1`

## Remediation

Upgrade past the affected range:

- `nsd 4.15.1`