Cyber Resilience

CVE-2026-55708

Nlnetlabs Unbound 1.6.0 – 1.25.2

Published
22 July 2026
Modified
24 July 2026
Patch / advisory
View advisory
CVSS Score v3.1 3.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:N
EPSS Score 0.0015 5th percentile
Risk Priority 25 floored blend · peak EPSS

Summary

CVE-2026-55708 is a low-severity Initialization of a Resource with an Insecure Default (CWE-1188) vulnerability in Nlnetlabs Unbound. Its CVSS base score is 3.1 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Default Accounts (T1078.001); ranked at the 5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to CM-2 (Baseline Configuration) and CM-6 (Configuration Settings) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

In NLnet Labs Unbound 1.6.0 up to and including 1.25.1, the 'view_local_data' and 'view_local_datas' commands of 'unbound-control' create a bare local zones tree for an already configured named view when the view is configured with no local data to begin…

more

with. However, the creation through the control interface omits adding the default-protected zones (e.g., RFC 1918 reverse, AS112 zones, .onion, .localhost). Once the local zone tree exists without the defaults, every query for a default-protected name from a client mapped to that view escapes to the public DNS via the iterator instead of being answered locally, bypassing local policy expectations.

CWE(s)
CWE-1188

Related Threats

MITRE ATT&CK Enterprise Techniques

T1078.001 Default Accounts Stealth
Adversaries may obtain and abuse credentials of a default account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion.
attack.mitre.org →
T1078 Valid Accounts Stealth
Adversaries may obtain and abuse credentials of existing accounts as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion.
attack.mitre.org →
T1133 External Remote Services Persistence
Adversaries may leverage external-facing remote services to initially access and/or persist within a network.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1542.002 Component Firmware Stealth
Adversaries may modify component firmware to persist on systems.
attack.mitre.org →
T1556 Modify Authentication Process Defense Impairment
Adversaries may modify authentication mechanisms and processes to access user credentials or enable otherwise unwarranted access to accounts.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-50251Same product: Nlnetlabs Unbound
CVE-2026-42955Same product: Nlnetlabs Unbound
CVE-2026-33278Same product: Nlnetlabs Unbound
CVE-2026-52863Same product: Nlnetlabs Unbound
CVE-2026-50248Same product: Nlnetlabs Unbound
CVE-2026-44687Same product: Nlnetlabs Unbound
CVE-2026-55991Same product: Nlnetlabs Unbound
CVE-2026-42534Same product: Nlnetlabs Unbound
CVE-2026-50046Same product: Nlnetlabs Unbound
CVE-2026-44690Same product: Nlnetlabs Unbound

Affected Assets

nlnetlabs
unbound
1.6.0 — 1.25.2

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 13 hardening rules · 7 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V14.3.2
  • V6.3.2
  • V11.3.1
  • V13.2.3

Mitigating Controls (NIST 800-53 r5) AI

CM-2 Baseline Configuration good match

Baseline configuration directly requires documenting and maintaining secure initial settings instead of insecure defaults.

CM-6 Configuration Settings good match

Configuration settings mandate the most restrictive values be applied at initialization, eliminating reliance on insecure factory defaults.

AC-6 Least Privilege partial match

Least privilege reduces the blast radius of any insecure default permissions that remain after initialization.

SA-8 Security and Privacy Engineering Principles partial match

Security engineering principles include explicit requirements for secure defaults during resource initialization and design.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-01 full match
prevents

Hardened baselines and configuration management directly replace insecure defaults with secure settings.

PR.PS-06 mostly match
prevents

Secure development practices include designing products with secure defaults rather than insecure ones.

ID.RA-09 partial match
prevents

Pre-acquisition integrity checks can reject products known to ship with insecure defaults.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.9 Configuration management mostly match
prevents

Mandating secure baseline templates and immediate replacement of vendor defaults directly stops systems from being deployed with insecure factory settings that attackers can exploit.

A.8.32 Change management partial match
prevents

Requiring documented specification, testing, and acceptance of changes ensures that new or modified components are not initialized with insecure default settings that would otherwise be left in production.

A.5.21 Managing information security in the ICT supply chain none match
none

Requiring suppliers to document secure configuration and implemented security functions reduces the likelihood that products will be initialised with insecure default settings.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (1 rule)
  • V-248823 OL 8 must not have the telnet-server package installed. prevents CWE-1188
RHEL 7 (1 rule)
  • V-204627 SNMP community strings on the Red Hat Enterprise Linux operating system must be changed from the default. prevents CWE-1188
Ubuntu 22.04 (1 rule)
  • V-260529 Ubuntu 22.04 LTS must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements. prevents CWE-1188
Ubuntu 24.04 (1 rule)
  • V-270708 Ubuntu 24.04 LTS must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements. prevents CWE-1188
Windows Server 2016 (1 rule)
  • V-224972 Active Directory Group Policy objects must have proper access control permissions. prevents CWE-1188
Windows Server 2019 (1 rule)
  • V-205741 Windows Server 2019 Active Directory Group Policy objects must have proper access control permissions. prevents CWE-1188

References