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Public proof of conceptFix available

CVE-2026-81642

A public proof of concept exists; no exploitation attested.

  • Published2026-09-16
  • Fixed in1.26.1
  • WeaknessCWE-122

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-09-1609:17CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-81642?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-81642?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Nlnetlabs unbound
BranchAffectedFixed in
1.26< 1.26.11.26.1

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • unboundAlmaLinux:10all versions · fixed in 1.24.2-7.el10_2.6and 6 other packages
  • unboundAlmaLinux:9all versions · fixed in 1.24.2-3.el9_8.8and 4 other packages
  • unboundAlmaLinux:8all versions · fixed in 1.16.2-5.14.el8_10.4and 3 other packages

Vendor advisories

  • CVE-2026-81642 Red Hat Product Security386 products fixed · 5 known affected

    unbound: Unbound: Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY

    unbound as a component of Red Hat Enterprise Linux 6 · unbound-devel as a component of Red Hat Enterprise Linux 6 · unbound-libs as a component of Red Hat Enterprise Linux 6 · +2 more

  • RHSA-2026:72264 Red Hat Product Security38 products fixed

    Red Hat Security Advisory: unbound security update

  • RHSA-2026:72199 Red Hat Product Security37 products fixed

    Red Hat Security Advisory: unbound security update

  • RHSA-2026:72183 Red Hat Product Security14 products fixed

    Red Hat Security Advisory: unbound security update

  • RHSA-2026:72110 Red Hat Product Security14 products fixed

    Red Hat Security Advisory: unbound security update

  • RHSA-2026:71487 Red Hat Product Security63 products fixed

    Red Hat Security Advisory: unbound security update

7 more advisories

Full record on NVD

Fix

  1. Update Nlnetlabs unbound to 1.26.1
  2. Vendor fix Red Hat Product Security RHSA-2026:72264 · 38 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  3. Vendor fix Red Hat Product Security RHSA-2026:68590 · 17 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
  4. Workaround from the vendor Red Hat Product Security RHSA-2026:72264 · 38 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Advisories and patches

Detection

read 2026-10-23 19:25 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
1 repository, unverifiedsuominen/CVE-2026-81642
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2026-09-16
  • OpenCVESSVC decisionnone—
  • CNACVSS 4.09.1read 2026-10-23
  • NVDCVSS 3.19.8read 2026-10-23
  • CNAweakness (CWE)CWE-122read 2026-10-23
  • FIRST EPSSEPSS score1.0 %2026-10-23
  • PoC-in-GitHubproof of concept1read 2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 4.0 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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Red
Published
2026-09-16
Last Modified
2026-09-22
NVD status
Analyzed

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.

Is CVE-2026-81642 actively exploited?

Active exploitation of CVE-2026-81642 has not been confirmed. Its EPSS score was 1.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-81642?

CVE-2026-81642 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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