Description
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 products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| NLnet Labs | NSD | 4.8.0 – < 4.15.1 | 4.15.1 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | nsd | 4.15.1-1 | — |
| Debian 13 | nsd | No fix yet | — |
| Debian 12 | nsd | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | nsd | No fix yet | — |
Show 6 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | nsd | No fix yet | — |
| Ubuntu Pro 24.04 LTS | nsd | No fix yet | — |
| Ubuntu Pro 22.04 LTS | nsd | No fix yet | — |
| Ubuntu Pro 20.04 LTS | nsd | No fix yet | — |
| Ubuntu Pro 18.04 LTS | nsd | No fix yet | — |
| Ubuntu Pro 16.04 LTS | nsd | No fix yet | — |
Advisories 1
- WID-SEC-2026-3663 OpenBSD: Mehrere Schwachstellen BSI CERT-Bund (WID) · Sep 29, 2026
References
- https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-19538.txt vendor-advisory