CVE-2026-19538

Bypass of BLOCKED ACL items on proxy protocol port over TCP or TLS

Published Aug 26, 2026 CVSS 4.0 · 8.2 High EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

This issue is fixed in 4.15.1 and all later versions.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
CPEs cpe:2.3:a:nlnetlabs:nsd:*:*:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}

Type Values Removed Values Added
First Time appeared Nlnetlabs
Nlnetlabs nsd
Vendors & Products Nlnetlabs
Nlnetlabs nsd
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Bypass of BLOCKED ACL items on proxy protocol port over TCP or TLS
Weaknesses CWE-290
CWE-672
References
Metrics cvssV4_0

{'score': 8.2, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
NLnet Labs
Published
Updated
Aug 26, 2026, 2:00 PM
Reserved
Aug 11, 2026, 10:27 AM
Status
Analyzed
Published
Aug 26, 2026, 9:16 AM
Modified
Sep 8, 2026, 7:59 PM