CVE-2026-33278

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-05-20. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 9.8Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
9.8
EG Score
9.8(medium)
EPSS
66.4%
KEV
Not listed

Published

May 20, 2026

Last Modified

June 30, 2026

Advisory Details (7)

Auto-updated Jul 12, 2026
Patch available. Sources: redhat.
redhat Patch Available

Affected: Red Hat Enterprise Linux 6",

https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33278.json
redhat Patch Available

2479808 – (CVE-2026-33278) CVE-2026-33278 unbound: Unbound DNSSEC Validator Use-After-Free via Deep Copy Pointer Overwrite Leading to DoS and Possible Remote Code Execution

Affected: Red Hat Enterprise Linux 10

https://bugzilla.redhat.com/show_bug.cgi?id=2479808
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-33278
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:24369
redhat Patch Available

Affected: Red Hat Enterprise Linux 10.

https://access.redhat.com/errata/RHSA-2026:23231
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:19752
generic
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt

Vendor Advisories for CVE-2026-33278(4)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuunbound-host (1.24.2-1ubuntu2.1) @ resolute2026-06-29ubuntu
redhatunbound-0:1.24.2-3.el9_8.12026-06-08redhat
redhatunbound-0:1.24.2-7.el10_2.12026-06-04redhat
redhatunbound-main-1.25.1-0.1.hum12026-05-20redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(2)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 9× in last 7d / 175× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 415 total refreshes for this CVE.

  1. 2026-07-11 08:27 UTCEPSS rescore
  2. 2026-07-09 19:10 UTCEPSS rescore
  3. 2026-07-08 15:15 UTCEPSS rescore
  4. 2026-07-07 13:46 UTCEPSS rescore
  5. 2026-07-06 16:27 UTCEPSS rescore
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  7. 2026-07-06 02:23 UTCEPSS rescore
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  9. 2026-07-05 02:30 UTCEPSS rescore
  10. 2026-07-04 06:31 UTCEPSS rescore
  11. 2026-07-01 15:06 UTCEPSS rescore
  12. 2026-06-30 23:22 UTCEPSS rescore
  13. 2026-06-29 20:30 UTCEG score recompute
  14. 2026-06-29 20:30 UTCVendor advisory
  15. 2026-06-29 20:30 UTCGHSA enrichment
  16. 2026-06-29 14:06 UTCEPSS rescore
  17. 2026-06-29 14:06 UTCEPSS rescore
  18. 2026-06-28 14:07 UTCEPSS rescore
  19. 2026-06-28 14:07 UTCEPSS rescore
  20. 2026-06-28 12:43 UTCEG score recompute
  21. 2026-06-28 12:43 UTCVendor advisory
  22. 2026-06-28 12:43 UTCGHSA enrichment
  23. 2026-06-28 08:44 UTCEG score recompute
  24. 2026-06-28 08:44 UTCVendor advisory
  25. 2026-06-28 08:44 UTCGHSA enrichment
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  1. 2026-06-28 04:56 UTCEPSS rescore
  2. 2026-06-28 04:56 UTCEPSS rescore
  3. 2026-06-28 04:49 UTCEG score recompute
  4. 2026-06-28 04:49 UTCVendor advisory
  5. 2026-06-28 04:49 UTCGHSA enrichment
  6. 2026-06-28 00:49 UTCEG score recompute
  7. 2026-06-28 00:49 UTCVendor advisory
  8. 2026-06-28 00:49 UTCGHSA enrichment
  9. 2026-06-27 20:17 UTCEG score recompute
  10. 2026-06-27 20:17 UTCVendor advisory
  11. 2026-06-27 20:17 UTCGHSA enrichment
  12. 2026-06-27 12:22 UTCEG score recompute
  13. 2026-06-27 12:22 UTCVendor advisory
  14. 2026-06-27 12:22 UTCGHSA enrichment
  15. 2026-06-27 07:26 UTCEG score recompute
  16. 2026-06-27 07:26 UTCVendor advisory
  17. 2026-06-27 07:26 UTCGHSA enrichment
  18. 2026-06-27 03:08 UTCEPSS rescore
  19. 2026-06-26 23:30 UTCEG score recompute
  20. 2026-06-26 23:30 UTCVendor advisory
  21. 2026-06-26 23:30 UTCGHSA enrichment
  22. 2026-06-26 19:35 UTCEG score recompute
  23. 2026-06-26 19:35 UTCVendor advisory
  24. 2026-06-26 19:35 UTCGHSA enrichment
  25. 2026-06-26 03:49 UTCEG score recompute
  26. 2026-06-26 03:49 UTCVendor advisory
  27. 2026-06-26 03:49 UTCGHSA enrichment
  28. 2026-06-25 20:09 UTCEG score recompute
  29. 2026-06-25 20:09 UTCVendor advisory
  30. 2026-06-25 20:09 UTCGHSA enrichment
  31. 2026-06-25 16:15 UTCEG score recompute
  32. 2026-06-25 16:15 UTCVendor advisory
  33. 2026-06-25 16:15 UTCGHSA enrichment
  34. 2026-06-25 13:49 UTCEPSS rescore
  35. 2026-06-25 13:49 UTCEPSS rescore
  36. 2026-06-24 14:05 UTCEPSS rescore
  37. 2026-06-23 21:33 UTCEPSS rescore
  38. 2026-06-23 21:33 UTCEPSS rescore
  39. 2026-06-22 14:25 UTCEPSS rescore
  40. 2026-06-22 14:25 UTCEPSS rescore
  41. 2026-06-21 14:56 UTCEPSS rescore
  42. 2026-06-21 14:56 UTCEPSS rescore
  43. 2026-06-21 01:59 UTCEPSS rescore
  44. 2026-06-19 19:25 UTCEPSS rescore
  45. 2026-06-19 19:25 UTCEPSS rescore
  46. 2026-06-18 17:52 UTCEPSS rescore
  47. 2026-06-18 17:52 UTCEPSS rescore
  48. 2026-06-18 03:52 UTCEG score recompute
  49. 2026-06-18 03:52 UTCVendor advisory
  50. 2026-06-18 03:52 UTCGHSA enrichment
  51. 2026-06-17 23:58 UTCEG score recompute
  52. 2026-06-17 23:58 UTCVendor advisory
  53. 2026-06-17 23:58 UTCGHSA enrichment
  54. 2026-06-17 20:04 UTCEG score recompute
  55. 2026-06-17 20:04 UTCVendor advisory
  56. 2026-06-17 20:04 UTCGHSA enrichment
  57. 2026-06-17 17:53 UTCEPSS rescore
  58. 2026-06-17 15:34 UTCEG score recompute
  59. 2026-06-17 15:34 UTCVendor advisory
  60. 2026-06-17 15:34 UTCGHSA enrichment
  61. 2026-06-17 11:26 UTCEG score recompute
  62. 2026-06-17 11:26 UTCVendor advisory
  63. 2026-06-17 11:26 UTCGHSA enrichment
  64. 2026-06-17 04:04 UTCEG score recompute
  65. 2026-06-17 04:04 UTCVendor advisory
  66. 2026-06-17 04:04 UTCGHSA enrichment
  67. 2026-06-17 00:10 UTCEG score recompute
  68. 2026-06-17 00:10 UTCVendor advisory
  69. 2026-06-17 00:10 UTCGHSA enrichment
  70. 2026-06-16 20:15 UTCEG score recompute
  71. 2026-06-16 20:15 UTCVendor advisory
  72. 2026-06-16 20:15 UTCGHSA enrichment
  73. 2026-06-16 17:52 UTCEPSS rescore
  74. 2026-06-16 10:48 UTCEG score recompute
  75. 2026-06-16 10:48 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-33278?
CVE-2026-33278 is a critical vulnerability published on May 20, 2026. 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…
When was CVE-2026-33278 disclosed?
CVE-2026-33278 was first published in the National Vulnerability Database on May 20, 2026, with the most recent update on June 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33278 actively exploited?
CVE-2026-33278 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 66.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-33278?
CVE-2026-33278 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-33278?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33278, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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