CVE-2026-81642
Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
No known exploitation. EPSS puts it in the 54th percentile. A vendor fix is available.
What to do
The vendor has published a fix. Version details are below where the sources state them.
Steps
Written by AI from the record- Check whether your DNS resolver runs unbound, whether DNSSEC validation is enabled, and whether its version is 1.26.0 or earlier.
- Upgrade unbound to version 1.26.1.
- If you cannot upgrade promptly, apply the vendor’s temporary workaround and restrict the resolver to trusted networks.
- Review resolver crashes and unusual DNS responses after remediation.
What it is
From the CVE record
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.
In plain language
Written by AI from the recordunbound 1.26.0 or earlier can be taken over or knocked offline by a malicious DNS zone, so businesses running it with DNSSEC validation enabled should act now.
Heap buffer overflow in unbound’s DNSSEC validator while digesting a crafted DNSKEY with a self-referential compression pointer, enabling unauthenticated network DoS and possible RCE.
If you're affected
- DNS resolver outage
- Server takeover
- Network disruption
- Service downtime
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
0.8% chance of exploitation activity in the next 30 days, which ranks it in the 54th percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
- Attention now
Rising, driven by in-the-wild reports.
Lifecycle
12 events over 6 days, from the signal feeds we watch.
- Patch availableworkaround available, record updated
- Patch availablepatch available, patch available, published, weakness classified, att&ck mapped, record updated, record updated, record updated
Affected products
Technical detail
CVSS 3.1 vector
Open in the CVSS calculatorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Scored 9.8 by NVD.
How it is reached
- Attack Vector NetworkExploitable remotely over the network without any special conditions
- Attack Complexity LowNo special conditions — the attack can be reliably reproduced
- Privileges Required NoneNo authentication required — anyone can exploit this
- User Interaction NoneNo user interaction needed — fully automated exploitation
Scope
- Scope UnchangedImpact is limited to the vulnerable component itself
Impact if exploited
- Confidentiality HighTotal information disclosure — all data in the component is compromised
- Integrity HighTotal loss of integrity — attacker can modify any data in the component
- Availability HighTotal denial of service — the component is completely unavailable
Weaknesses
ATT&CK techniques
Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.
- Privilege EscalationT1068Exploitation for Privilege Escalationhigh confidence
Sources
Watch the software you run.
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We'll flag the next CVE, public exploit or patch for Unbound, not every advisory.
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