Buffer overflow in Nlnet Labs Unbound
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.010 (61.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 62nd percentile — 61.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- www.nlnetlabs.nl/downloads/unbound/CVE-2026-81642.txt (vendor-advisory, Patch, Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-81642?
- CVE-2026-81642 is a critical-severity vulnerability in Nlnet Labs Unbound, classified under Heap-based Buffer Overflow. CVSS score: 9.8/10. Published 2026-09-16.
- How severe is CVE-2026-81642?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2026-81642 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.