Review reviewHigh

CVE-2026-42944

NLnet Labs Unbound, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8

NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the enc...

CVSS: 8.7
EPSS: 0.84%
CISA KEV: Not listed
Published: 2026.05.20

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.84%

Technical severityCVSS 8.7

Vulnerability overview

Affected product and versions

Product: NLnet Labs Unbound, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8
Affected versions: >= 1.14.0 < 1.25.1
Fixed versions: 1.25.1

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that NLnet Labs Unbound, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/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
CWE: CWE-197, CWE-787