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 — 4 sources updated this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: None knownExposed: 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 PROB
1%
EPSS %ILE
52%
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 (1.5.8-1ubuntu1.1+esm3) @ xenial2026-07-26ubuntu
ubuntuunbound-host (1.24.2-1ubuntu2.1) @ resolute2026-07-26ubuntu
redhatunbound-0:1.24.2-3.el9_8.12026-06-08redhat
redhatunbound-0:1.16.2-5.11.el8_102026-06-08redhat
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 12× in last 7d / 42× 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 176 total refreshes for this CVE.

  1. 2026-07-26 14:54 UTCEPSS rescore
  2. 2026-07-26 14:54 UTCEPSS rescore
  3. 2026-07-26 08:15 UTCEG score recompute
  4. 2026-07-26 08:15 UTCVendor advisory
  5. 2026-07-26 08:15 UTCGHSA enrichment
  6. 2026-07-25 14:18 UTCEPSS rescore
  7. 2026-07-24 14:17 UTCEPSS rescore
  8. 2026-07-23 14:18 UTCEPSS rescore
  9. 2026-07-23 03:12 UTCEG score recompute
  10. 2026-07-22 14:08 UTCEPSS rescore
  11. 2026-07-21 15:24 UTCEPSS rescore
  12. 2026-07-20 17:08 UTCEPSS rescore
  13. 2026-07-19 14:31 UTCEPSS rescore
  14. 2026-07-19 02:29 UTCEPSS rescore
  15. 2026-07-18 10:04 UTCEPSS rescore
  16. 2026-07-17 22:59 UTCOSV refresh
  17. 2026-07-16 17:03 UTCEPSS rescore
  18. 2026-07-15 16:57 UTCEPSS rescore
  19. 2026-07-15 02:00 UTCEPSS rescore
  20. 2026-07-13 22:30 UTCEPSS rescore
  21. 2026-07-13 06:13 UTCEPSS rescore
  22. 2026-07-12 05:46 UTCEPSS rescore
  23. 2026-07-11 08:27 UTCEPSS rescore
  24. 2026-07-09 19:10 UTCEPSS rescore
  25. 2026-07-08 15:16 UTCEPSS rescore
Show 75 more
  1. 2026-07-07 13:46 UTCEPSS rescore
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 02:23 UTCEPSS rescore
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-05 02:30 UTCEPSS rescore
  6. 2026-07-04 06:31 UTCEPSS rescore
  7. 2026-07-01 15:06 UTCEPSS rescore
  8. 2026-06-30 23:22 UTCEPSS rescore
  9. 2026-06-29 20:30 UTCVendor advisory
  10. 2026-06-29 20:30 UTCGHSA enrichment
  11. 2026-06-29 14:06 UTCEPSS rescore
  12. 2026-06-28 14:07 UTCEPSS rescore
  13. 2026-06-28 07:57 UTCVendor advisory
  14. 2026-06-28 07:57 UTCGHSA enrichment
  15. 2026-06-28 04:56 UTCEPSS rescore
  16. 2026-06-27 20:16 UTCVendor advisory
  17. 2026-06-27 20:16 UTCGHSA enrichment
  18. 2026-06-27 07:26 UTCVendor advisory
  19. 2026-06-27 07:26 UTCGHSA enrichment
  20. 2026-06-27 03:08 UTCEPSS rescore
  21. 2026-06-26 19:35 UTCVendor advisory
  22. 2026-06-26 19:35 UTCGHSA enrichment
  23. 2026-06-26 03:48 UTCVendor advisory
  24. 2026-06-26 03:48 UTCGHSA enrichment
  25. 2026-06-25 16:09 UTCVendor advisory
  26. 2026-06-25 16:08 UTCGHSA enrichment
  27. 2026-06-25 13:49 UTCEPSS rescore
  28. 2026-06-25 13:49 UTCEPSS rescore
  29. 2026-06-24 14:05 UTCEPSS rescore
  30. 2026-06-23 21:33 UTCEPSS rescore
  31. 2026-06-22 14:25 UTCEPSS rescore
  32. 2026-06-22 14:25 UTCEPSS rescore
  33. 2026-06-21 14:56 UTCEPSS rescore
  34. 2026-06-21 14:56 UTCEPSS rescore
  35. 2026-06-21 01:59 UTCEPSS rescore
  36. 2026-06-19 19:25 UTCEPSS rescore
  37. 2026-06-18 17:52 UTCEPSS rescore
  38. 2026-06-18 17:52 UTCEPSS rescore
  39. 2026-06-17 22:42 UTCVendor advisory
  40. 2026-06-17 22:42 UTCGHSA enrichment
  41. 2026-06-17 17:53 UTCEPSS rescore
  42. 2026-06-17 11:26 UTCVendor advisory
  43. 2026-06-17 11:26 UTCGHSA enrichment
  44. 2026-06-16 21:41 UTCVendor advisory
  45. 2026-06-16 21:40 UTCGHSA enrichment
  46. 2026-06-16 17:52 UTCEPSS rescore
  47. 2026-06-16 10:47 UTCVendor advisory
  48. 2026-06-16 10:46 UTCGHSA enrichment
  49. 2026-06-15 22:55 UTCVendor advisory
  50. 2026-06-15 22:55 UTCGHSA enrichment
  51. 2026-06-15 17:49 UTCEPSS rescore
  52. 2026-06-15 07:51 UTCVendor advisory
  53. 2026-06-15 07:51 UTCGHSA enrichment
  54. 2026-06-14 20:14 UTCVendor advisory
  55. 2026-06-14 20:14 UTCGHSA enrichment
  56. 2026-06-14 09:22 UTCVendor advisory
  57. 2026-06-14 09:22 UTCGHSA enrichment
  58. 2026-06-13 23:00 UTCEPSS rescore
  59. 2026-06-13 22:30 UTCVendor advisory
  60. 2026-06-13 22:30 UTCGHSA enrichment
  61. 2026-06-13 08:38 UTCVendor advisory
  62. 2026-06-13 08:37 UTCGHSA enrichment
  63. 2026-06-12 23:12 UTCEPSS rescore
  64. 2026-06-12 23:12 UTCEPSS rescore
  65. 2026-06-12 21:44 UTCVendor advisory
  66. 2026-06-12 21:43 UTCGHSA enrichment
  67. 2026-06-12 10:51 UTCVendor advisory
  68. 2026-06-12 10:51 UTCGHSA enrichment
  69. 2026-06-11 23:59 UTCVendor advisory
  70. 2026-06-11 23:59 UTCGHSA enrichment
  71. 2026-06-11 14:00 UTCEPSS rescore
  72. 2026-06-11 13:07 UTCVendor advisory
  73. 2026-06-11 13:06 UTCGHSA enrichment
  74. 2026-06-11 02:14 UTCVendor advisory
  75. 2026-06-11 02:14 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 1% probability of exploitation in the next 30 days, which ranks it in the top 47.9% of all scored CVEs.
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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