CVE-2026-42944

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 encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42944.txt	Mitigation Vendor Advisory
https://access.redhat.com/errata/RHSA-2026:19752
https://access.redhat.com/errata/RHSA-2026:23231
https://access.redhat.com/errata/RHSA-2026:24365
https://access.redhat.com/errata/RHSA-2026:24369
https://access.redhat.com/security/cve/CVE-2026-42944
https://bugzilla.redhat.com/show_bug.cgi?id=2479774
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42944.json

Configurations

Configuration 1 (hide)

cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-05-20 10:16

Updated : 2026-08-26 13:19

NVD link : CVE-2026-42944

Mitre link : CVE-2026-42944

CVE.ORG link : CVE-2026-42944

JSON object : View

Products Affected

nlnetlabs

unbound

CWE

CWE-197

Numeric Truncation Error

CWE-787

Out-of-bounds Write

CWE-131

Incorrect Calculation of Buffer Size

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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 encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation."}, {"lang": "es", "value": "NLnet Labs Unbound 1.14.0 hasta la versi\u00f3n 1.25.0 inclusive tiene una vulnerabilidad que resulta en un desbordamiento de mont\u00edculo al codificar m\u00faltiples opciones NSID y/o DNS Cookie EDNS y/o EDNS Padding en el paquete de respuesta. Las opciones relevantes ('nsid', 'answer-cookie', 'pad-responses' (predeterminado)) deben estar habilitadas para que la vulnerabilidad sea explotada. Un adversario que puede consultar Unbound puede explotar la vulnerabilidad adjuntando m\u00faltiples opciones NSID y/o DNS Cookie EDNS y/o EDNS Padding a la consulta. Un fallo en el c\u00e1lculo del tama\u00f1o del campo EDNS trunca el valor correcto, lo que permite al codificador desbordar el espacio disponible al escribir. Esos dos combinados conducen a una escritura de desbordamiento de mont\u00edculo de datos controlados por Unbound y eventualmente a un fallo. Unbound 1.25.1 contiene un parche con una correcci\u00f3n para desduplicar las opciones EDNS y una correcci\u00f3n para evitar la truncaci\u00f3n del c\u00e1lculo del tama\u00f1o del campo EDNS."}], "lastModified": "2026-08-26T13:19:01.207", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "94679303-2382-42F1-8BFF-FD02D0444EE6", "versionEndExcluding": "1.25.1", "versionStartIncluding": "1.14.0"}], "operator": "OR"}]}], "sourceIdentifier": "sep@nlnetlabs.nl"}