CVE-2026-81642: unbound Heap Overflow — Fix

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.

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CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0096

Probability of exploitation

0.61%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-122 CWE-122

Affected Products

Vendor	Product	Versions
nlnetlabs	unbound	< 1.26.1

References

Advisories & Patches

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81642.txt

Frequently Asked Questions

What is CVE-2026-81642? +

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. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-81642? +

CVE-2026-81642 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0096, placing it in the 1th percentile for exploitation probability.

What products are affected by CVE-2026-81642? +

CVE-2026-81642 affects products from nlnetlabs, specifically: unbound. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-81642? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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