Description
In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that enables denial of service and possible remote code execution as a result of digesting DNSKEYs. A DNSKEY with an owner compression pointer to its own RDATA can overflow the digest buffer. Remote code execution is possible through attacker controlled data. An adversary can exploit the vulnerability by controlling a malicious zone and querying a vulnerable Unbound.
Published: 2026-09-16
Score: 9.1 Critical
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

Vendor Solution

This issue is fixed starting with version 1.26.1

Tracking

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Advisories
Source ID Title
Debian DSA Debian DSA DSA-6507-1 unbound security update
History

Fri, 18 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Critical


Thu, 17 Sep 2026 21:00:00 +0000

Type Values Removed Values Added
First Time appeared Nlnetlabs
Nlnetlabs unbound
Vendors & Products Nlnetlabs
Nlnetlabs unbound

Wed, 16 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Wed, 16 Sep 2026 08:45:00 +0000

Type Values Removed Values Added
Description In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that enables denial of service and possible remote code execution as a result of digesting DNSKEYs. A DNSKEY with an owner compression pointer to its own RDATA can overflow the digest buffer. Remote code execution is possible through attacker controlled data. An adversary can exploit the vulnerability by controlling a malicious zone and querying a vulnerable Unbound.
Title Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
Weaknesses CWE-122
References
Metrics cvssV4_0

{'score': 9.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red'}


Subscriptions

Nlnetlabs Unbound
cve-icon MITRE

Status: PUBLISHED

Assigner: NLnet Labs

Published:

Updated: 2026-09-16T14:32:16.825Z

Reserved: 2026-09-07T14:06:21.956Z

Link: CVE-2026-81642

cve-icon Vulnrichment

Updated: 2026-09-16T14:30:26.931Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-16T09:17:06.320

Modified: 2026-09-16T19:41:10.423

Link: CVE-2026-81642

cve-icon Redhat

Severity : Critical

Publid Date: 2026-09-16T08:30:58Z

Links: CVE-2026-81642 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-18T12:45:08Z

Weaknesses