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TI-2026-32579 Aliases CVE-2026-44687GHSA-x324-pxwv-r76h

Off-by-one error in 'harden-below-nxdomain' logic can shadow a stub/forward zone by a legitimate parent's NXDOMAIN

Priority LOW 17CWE-193Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
None · None · Low
Fix status
Partial Red Hat: 1 fixed, 5 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.

Summary

In NLnet Labs Unbound 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an intermediate labed below a DNSSEC signed zone could be shadowed by the intermediate label's secure NXDOMAIN answer from the parent. This is caused by an off-by-one error in 'harden-below-nxdomain' logic; enabled by default. It effectively bypasses the configuration and the configured stub/forward zone is never contacted. 'harden-below-nxdomain' does an upward DNS cache walk together with a delegation point guard that does not allow NXDOMAIN synthesis above stub/forward zones. The guard tests the domain name but before stripping a label. This results in an iteration where the domain name equals the configured stub/forward zone apex that passes the guard, strips one more label, and probes the cache at the apex's immediate public parent. If that parent has a cached DNSSEC-secure NXDOMAIN, which it will for any private namespace nested two or more labels under a signed public name, the walk returns it and the configured stub/forward upstream is never contacted. This can only be triggered by the query for the intermediate label (between the stub/forward apex and the DNSSEC parent zone).

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00218 12th percentileScored 2026-11-07
Fix Partial Unbound (NLnet Labs): 1.25.2Red Hat: 1 advisoryRed Hat: 1 fixed, 5 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
NLnet LabsUnbound1.13.2 to before 1.25.21.25.2Patch availableCNA
  • Unbound VendorNLnet Labs Affected 1.13.2 to before 1.25.2 Fixed in 1.25.2 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*1.13.2 to before 1.25.2VulnerableNLNETLABS
  • cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* Versions 1.13.2 to before 1.25.2 Vulnerable ·NLNETLABS

Remediation

  • Fix · CNA Unbound (NLnet Labs) Fixed in 1.25.2

Red Hat 1 advisory

  • RHSA-2026:43588 Released 2026-07-22 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images python3-unbound-1.25.2-0.1.hum1@aarch64, python3-unbound-1.25.2-0.1.hum1@x86_64, unbound-1.25.2-0.1.hum1@aarch64 +14

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    NLnet Labs Unbound 1.25.2

    24 records Highest priority Priority LOW 24 LOW

    Other records, highest priority first

    • TI-2026-40374 'dns-error-reporting: yes' leads to stack buffer overflowPriority LOW 39
    • TI-2026-29375 Packet of death for DNSCrypt over TCPPriority LOW 39
    • TI-2026-25166 Remote DNS-over-QUIC denial of service due to `quic-size` budget bypassPriority LOW 39
    Show all 24 records →

Vendor assessments

Red Hat

Red Hat rating: Low. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 10AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 8AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 9AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 4AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 5AffectedNo fix yet: Fix deferred
Red Hat Hardened ImagesFixed RHSA-2026:43588
Not affected: 3 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat OpenShift Container Platform 4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-44687
  2. 2026-10-03 Alias added: GHSA-x324-pxwv-r76h
  3. 2026-11-06 Affected versions changed · Red Hat

References

Advisory 1

  • TI-2026-25690 Possible arbitrary code execution during DNSSEC validation CVSS 4.0CRITICAL 9.1
  • TI-2026-56302 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY CVSS 4.0CRITICAL 9.1
  • TI-2026-31146 Crash during DNSSEC validation of malicious content CVSS 4.0HIGH 8.7
  • TI-2026-31135 Heap overflow with multiple NSID, COOKIE, PADDING EDNS options CVSS 4.0HIGH 8.7
  • TI-2026-36436 Routinator crashes on specifically crafted RRDP XML files CVSS 4.0HIGH 8.7
  • TI-2026-36433 Routinator exits when accepting an incoming HTTP or RTR connection fails CVSS 4.0HIGH 8.7
See all 96 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences