CVE-2026-81642

Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY

Published Sep 16, 2026 CVSS 4.0 · 9.1 Critical EPSS < 1% KEV · Not listed
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.

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
Ubuntu USN Ubuntu USN USN-8873-1 Unbound vulnerabilities
History
Type Values Removed Values Added
CPEs cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*
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

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

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

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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
NLnet Labs
Published
Updated
Sep 16, 2026, 2:32 PM
Reserved
Sep 7, 2026, 2:06 PM
Status
Analyzed
Published
Sep 16, 2026, 9:17 AM
Modified
Sep 22, 2026, 6:59 PM
Severity
Critical
Public date
Sep 16, 2026, 8:30 AM