CVE-2026-42959

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-05-20. NVD baseline CVSS 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
52.1%
KEV
Not listed

Published

May 20, 2026

Last Modified

July 24, 2026

Advisory Details (1)

Auto-updated May 20, 2026
No patch confirmed yet.
generic
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42959.txt

Vendor Advisories for CVE-2026-42959(4)

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

Patch Availability(6)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuunbound-host (1.4.22-1ubuntu4.14.04.3+esm3) @ trusty2026-06-29ubuntu
ubuntuunbound-host (1.24.2-1ubuntu2.1) @ resolute2026-06-29ubuntu
redhatunbound-0:1.16.2-5.11.el8_102026-06-08redhat
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(1)

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

Additional Vendor Advisories

(4)

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 / 47× 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 169 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-42959?
CVE-2026-42959 is a high vulnerability published on May 20, 2026. NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for…
When was CVE-2026-42959 disclosed?
CVE-2026-42959 was first published in the National Vulnerability Database on May 20, 2026, with the most recent update on July 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42959 actively exploited?
CVE-2026-42959 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 52.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42959?
CVE-2026-42959 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-42959?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42959, 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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