CVE-2026-33278
Possible arbitrary code execution during DNSSEC validation
Description
NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.
INFO
Published Date :
May 20, 2026, 10:16 a.m.
Last Modified :
July 24, 2026, 10:10 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 3.1 | HIGH | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | ||||
| CVSS 4.0 | CRITICAL | 206fc3a0-e175-490b-9eaa-a5738056c9f6 | ||||
| CVSS 4.0 | CRITICAL | [email protected] |
Solution
- Update Unbound to version 1.25.1 or later.
- Apply the vendor-provided patch for DNSSEC validation.
- Ensure correct pointer handling during deep copying.
- Validate DNSSEC responses for integrity.
Public PoC/Exploit Available at Github
CVE-2026-33278 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-33278.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-33278 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-33278
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
cPanel/WHM CVE auditor & patcher — May 2026 batch, zero dependencies.
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Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-33278 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-33278 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Translated by [email protected]
Jul. 24, 2026
Action Type Old Value New Value Added Translation Title: Unbound de NLnet Labs, Description: NLnet Labs Unbound 1.19.1 hasta la versión 1.25.0 inclusive tiene una vulnerabilidad en el validador DNSSEC que permite la denegación de servicio y posible ejecución remota de código como resultado de la copia profunda de una estructura de datos y la sobrescritura errónea de un puntero de destino. Un adversario puede explotar la vulnerabilidad controlando una zona firmada maliciosa y consultando un Unbound vulnerable. Cuando las subconsultas DS necesitan suspender la validación debido al agotamiento del presupuesto computacional de NSEC3 (introducido en Unbound 1.19.1), Unbound realiza copias profundas de los mensajes de respuesta para preservarlos durante la desasignación de la región de memoria. Un error de asignación de estructura sobrescribe el puntero del destino con el puntero del origen. Después de que se libera la región de la subconsulta, el validador reanudado desreferencia este puntero colgante, lo que provoca un fallo o potencialmente permite la ejecución de código arbitrario. Unbound 1.25.1 contiene un parche con una corrección para preservar el puntero correcto al realizar la copia profunda de la estructura de datos. -
CVE Modified by 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Jul. 15, 2026
Action Type Old Value New Value Changed Affected [{'cpes': ['cpe:/o:redhat:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::crb'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 7', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'defaultStatus': 'unaffected'}] [{'cpes': ['cpe:/o:redhat:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'versions': [{'status': 'unaffected', 'version': '0:1.24.2-7.el10_2.1', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'unbound', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'versions': [{'status': 'unaffected', 'version': '0:1.24.2-3.el9_8.1', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'unbound', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'versions': [{'status': 'unaffected', 'version': '1.25.1-0.1.hum1', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'unbound-main', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'packageName': 'unbound', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unknown'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 7', 'packageName': 'unbound', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'unbound', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'packageName': 'rhcos', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}] -
CVE Modified by 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Jun. 30, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:/o:redhat:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::crb'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 7', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'defaultStatus': 'unaffected'}] Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-416 Added Reference https://access.redhat.com/errata/RHSA-2026:19752 Added Reference https://access.redhat.com/errata/RHSA-2026:23231 Added Reference https://access.redhat.com/errata/RHSA-2026:24369 Added Reference https://access.redhat.com/security/cve/CVE-2026-33278 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2479808 Added Reference https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33278.json -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-33278', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-05-20T12:13:01.681597Z'} -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'NLnet Labs', 'product': 'Unbound', 'versions': [{'status': 'affected', 'version': '1.19.1', 'lessThan': '1.25.1', 'versionType': 'semver'}], 'defaultStatus': 'unaffected'}] -
Initial Analysis by [email protected]
May. 20, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* versions from (including) 1.19.1 up to (excluding) 1.25.1 Added Reference Type NLnet Labs: https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt Types: Mitigation, Vendor Advisory -
New CVE Received by [email protected]
May. 20, 2026
Action Type Old Value New Value Added Description NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure. Added CVSS V4.0 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 Added CWE CWE-416 Added CWE CWE-672 Added Reference https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt