CVE-2026-33278
No exploitation reported by the sources we read.
- Published2026-05-20
- Fixed in1.25.1
- WeaknessCWE-416 · CWE-672
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « 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
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.
Timeline
dates in UTC- 2026-05-2010:16CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-33278?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-33278?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 1.x | ≥ 1.19.1, < 1.25.1 | 1.25.1 | NVD |
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_2.1and 6 other packages
- unboundAlmaLinux:9all versions · fixed in 1.24.2-3.el9_8.1and 4 other packages
Vendor advisories
unbound: Unbound DNSSEC Validator Use-After-Free via Deep Copy Pointer Overwrite Leading to DoS and Possible Remote Code Execution
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
Red Hat Security Advisory: unbound security update
Red Hat Security Advisory: unbound security update
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
Fix
- Update Nlnetlabs unbound to 1.25.1
- Vendor fix Red Hat Product Security RHSA-2026:24369 · 63 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
- Vendor fix Red Hat Product Security RHSA-2026:19752 · 17 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
- No fix planned, says the vendor Red Hat Product Security CVE-2026-33278 · 5 productsOut of support scope
Advisories and patches
- www.nlnetlabs.nlMitigation · Vendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- CISA-ADPSSVC decisionnone2026-05-20
- OpenCVESSVC decisionnone—
- CNACVSS 4.09.1read 2026-10-23
- CNACVSS 3.18.1read 2026-10-23
- NVDCVSS 3.19.8read 2026-10-23
- CNAweakness (CWE)CWE-416, CWE-672read 2026-10-23
- FIRST EPSSEPSS score1.1 %2026-10-23
- OSVaffected packages—
- Microsoft MSRCadvisory—
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
- 2026-05-20
- Last Modified
- 2026-08-25
- NVD status
- Modified
- MSRC Title
- Possible arbitrary code execution during DNSSEC validation
Frequently asked questions
What is CVE-2026-33278?
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What is the CVSS score for CVE-2026-33278?
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Same product first, then the same vendor advisory and the same publication week.