CVE-2026-33278 (GCVE-0-2026-33278)

Vulnerability from cvelistv5 – Published: 2026-05-20 09:18 – Updated: 2026-07-15 01:06
VLAI
Title
Possible arbitrary code execution during DNSSEC validation
Summary
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.
Severity
9.1 (Critical)
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/U:Red
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-416 - Use After Free
  • CWE-672 - Operation on a Resource after Expiration or Release
Assigner
References
Impacted products
Vendor Product Version
NLnet Labs Unbound Affected: 1.19.1 , < 1.25.1 (semver)
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Red Hat Red Hat Enterprise Linux 10 Unaffected: 0:1.24.2-7.el10_2.1 , < * (rpm)
    cpe:/o:redhat:enterprise_linux:10.2
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Red Hat Red Hat Enterprise Linux 9 Unaffected: 0:1.24.2-3.el9_8.1 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:9
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Red Hat Red Hat Hardened Images Unaffected: 1.25.1-0.1.hum1 , < * (rpm)
    cpe:/a:redhat:hummingbird:1
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Red Hat Red Hat Enterprise Linux 6     cpe:/o:redhat:enterprise_linux:6
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Red Hat Red Hat Enterprise Linux 7     cpe:/o:redhat:enterprise_linux:7
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Red Hat Red Hat Enterprise Linux 8     cpe:/o:redhat:enterprise_linux:8
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Red Hat Red Hat OpenShift Container Platform 4     cpe:/a:redhat:openshift:4
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Date Public
2026-05-20 00:00
Credits
Qifan Zhang (Palo Alto Networks)
Show details on NVD website
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}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.