Unbound DNSKEY digest overflow can RCE resolvers
Direct answer
Unbound DNSKEY digest overflow can RCE resolvers, also tracked as CVE-2026-81642 / Unbound DNSKEY RCE is a critical-severity threat campaign HOL Guard tracked from Sep 16, 2026 to Sep 16, 2026, verified against 2 primary sources and last reviewed Sep 20, 2026. Active tracking has ended and the record remains published as a permanent historical research record.
NLnet Labs Unbound through 1.26.0 can overflow a digest buffer while validating a malicious DNSKEY (owner compression pointer into its own RDATA), enabling DoS and possible remote code execution when the resolver digests attacker-controlled zone data. Upgrade to Unbound 1.26.1 or later.
Also tracked as CVE-2026-81642 · Unbound DNSKEY RCE
- First observed
- Sep 16, 2026
- Last observed
- Sep 16, 2026
- Last reviewed
- Sep 20, 2026
- Tracking ended
- Sep 16, 2026
Record exports
Uncertainty and limitations
Read the evidence limits before acting on this record.
Remote code execution requires attacker-controlled zone data reaching the validator; packaging lag means distro packages may still ship 1.26.0 until rebuilds land.
- Only validating Unbound instances that process attacker-influenced DNSKEYs are in scope.
- OS package rebuilds may lag the upstream 1.26.1 tag.
- This campaign does not cover unrelated Unbound CVEs in the same release train.
Guard coverage and policy
What Guard's reviewed assertions do and do not claim for this campaign, and the reviewed starting points for defense.
No Guard coverage mapping or campaign-specific policy guidance is published for this record.
Safe next step. Campaign guidance is defensive context. It does not auto-apply policy or claim universal campaign coverage.
Timeline
Reviewed events, oldest first, each tied to a verified source.
- Disclosure
NLnet Labs published CVE-2026-81642 for Unbound DNSKEY digest buffer overflow.
- Vendor action
Fixed in Unbound 1.26.1 per vendor advisory.
- Update
HOL Guard published operator blog and social coverage for CVE-2026-81642.
Source:HOL Guard operator write-up
Publication clock: 100.3 hours from reviewed disclosure timestamp to HOL publication; 12-hour critical target; historical backfill outside target.
Reviewed artifacts
The specific artifacts this record concerns, as reviewed. Names and versions are shown as text; a registry link is not recorded here.
unbound@<=1.26.0nativepackage
Sources
Every claim on this record is traceable to the sources below.
Campaign questions, answered
NLnet Labs Unbound through 0 can overflow a digest buffer while validating a malicious DNSKEY (owner compression pointer into its own RDATA), enabling DoS and possible remote code execution when the resolver digests attacker-controlled zone data. HOL Guard tracked the campaign from Sep 16, 2026 to Sep 16, 2026.
No. Active tracking ended Sep 16, 2026; this page remains as a labeled historical research record and does not imply the threat is currently active.
The record cites 2 primary sources, names 1 reviewed artifact, and was last fully reviewed Sep 20, 2026 by HOL Guard Security Publishing. Its uncertainty and limitations are stated on the record itself.
Campaign guidance is defensive context. It does not auto-apply policy or claim universal campaign coverage.
The permalink above is permanent. The full record can be downloaded from this page as JSON, an artifact CSV, and a STIX 2.1 bundle, and corrections can be requested through the published correction path on the record. Remote code execution requires attacker-controlled zone data reaching the validator; packaging lag means distro packages may still ship 1.26.0 until rebuilds land.
Reviewed in full by HOL Guard Security Publishing.
- Published
- Last full review
- Last modified
Record HGTC-2026-8F7CDB8E