7.5High
Nlnetlabs Nsd
CVE-2026-19538
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.
What this means for your business
- It affects Nlnetlabs Nsd. It matters if your company, or a supplier that handles your data, runs it.
- An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
- FIRST's prediction model gives it a 0.3% chance of attack attempts being seen in the next 30 days, ranking above 22% of all known flaws.
What to do
- 1Check whether your company or your suppliers run Nlnetlabs Nsd, and which version. The affected versions are listed further down this page.
- 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.
Not sure if your company is exposed?
Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.
Scoring
- CVSS
- 7.5 (v3.1)
- Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N- CVSS v4
- 8.2
- Weakness
- CWE-290
- Assigned by
- sep@nlnetlabs.nl
Dates
- Published
- 2026-08-26
- Last modified
- 2026-09-08
- Sources
- NVD
Affected products
- Nlnetlabs Nsd4.8.0 - 4.15.1
As listed in the NVD configuration data. Not a statement about your estate.