CVE-2026-42923

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

Score 5.3 from GitHub Security Advisory published 2026-05-20. NVD baseline CVSS 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: None knownExposed: 0

A fix is available — apply it.

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: 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
Severity53% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
26%
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-2026-42923.txt

Vendor Advisories for CVE-2026-42923(3)

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

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuunbound-host (1.19.2-1ubuntu3.8) @ noble2026-07-26ubuntu
redhatunbound-main-1.25.1-1.hum12026-05-23redhat

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

(1)

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 / 40× 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 130 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 04:56 UTCEPSS rescore
  14. 2026-06-27 21:27 UTCVendor advisory
  15. 2026-06-27 21:27 UTCGHSA enrichment
  16. 2026-06-27 03:08 UTCEPSS rescore
  17. 2026-06-26 19:35 UTCVendor advisory
  18. 2026-06-26 19:35 UTCGHSA enrichment
  19. 2026-06-25 16:09 UTCVendor advisory
  20. 2026-06-25 16:09 UTCGHSA enrichment
  21. 2026-06-25 13:49 UTCEPSS rescore
  22. 2026-06-25 13:49 UTCEPSS rescore
  23. 2026-06-24 14:05 UTCEPSS rescore
  24. 2026-06-23 21:33 UTCEPSS rescore
  25. 2026-06-22 14:25 UTCEPSS rescore
  26. 2026-06-22 14:25 UTCEPSS rescore
  27. 2026-06-21 14:56 UTCEPSS rescore
  28. 2026-06-21 14:56 UTCEPSS rescore
  29. 2026-06-21 01:59 UTCEPSS rescore
  30. 2026-06-19 19:25 UTCEPSS rescore
  31. 2026-06-18 17:52 UTCEPSS rescore
  32. 2026-06-18 17:52 UTCEPSS rescore
  33. 2026-06-17 17:53 UTCEPSS rescore
  34. 2026-06-17 12:48 UTCVendor advisory
  35. 2026-06-17 12:48 UTCGHSA enrichment
  36. 2026-06-16 17:52 UTCEPSS rescore
  37. 2026-06-16 10:47 UTCVendor advisory
  38. 2026-06-16 10:47 UTCGHSA enrichment
  39. 2026-06-15 17:49 UTCEPSS rescore
  40. 2026-06-15 07:51 UTCVendor advisory
  41. 2026-06-15 07:51 UTCGHSA enrichment
  42. 2026-06-14 05:27 UTCVendor advisory
  43. 2026-06-14 05:27 UTCGHSA enrichment
  44. 2026-06-13 23:00 UTCEPSS rescore
  45. 2026-06-13 03:35 UTCVendor advisory
  46. 2026-06-13 03:34 UTCGHSA enrichment
  47. 2026-06-12 23:12 UTCEPSS rescore
  48. 2026-06-12 23:12 UTCEPSS rescore
  49. 2026-06-12 01:16 UTCVendor advisory
  50. 2026-06-12 01:16 UTCGHSA enrichment
  51. 2026-06-11 14:00 UTCEPSS rescore
  52. 2026-06-10 23:23 UTCVendor advisory
  53. 2026-06-10 23:23 UTCGHSA enrichment
  54. 2026-06-10 22:18 UTCEPSS rescore
  55. 2026-06-10 13:22 UTCEPSS rescore
  56. 2026-06-10 13:22 UTCEPSS rescore
  57. 2026-06-09 21:31 UTCVendor advisory
  58. 2026-06-09 21:31 UTCGHSA enrichment
  59. 2026-06-08 19:28 UTCVendor advisory
  60. 2026-06-08 19:28 UTCGHSA enrichment
  61. 2026-06-08 14:17 UTCEPSS rescore
  62. 2026-06-08 14:17 UTCEPSS rescore
  63. 2026-06-07 15:25 UTCEPSS rescore
  64. 2026-06-07 15:25 UTCEPSS rescore
  65. 2026-06-07 14:11 UTCVendor advisory
  66. 2026-06-07 14:11 UTCGHSA enrichment
  67. 2026-06-06 13:47 UTCEPSS rescore
  68. 2026-06-06 13:47 UTCEPSS rescore
  69. 2026-06-06 12:19 UTCVendor advisory
  70. 2026-06-06 12:19 UTCGHSA enrichment
  71. 2026-06-05 22:47 UTCEPSS rescore
  72. 2026-06-05 10:26 UTCVendor advisory
  73. 2026-06-05 10:26 UTCGHSA enrichment
  74. 2026-06-05 06:10 UTCEPSS rescore
  75. 2026-06-05 06:10 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-42923?
CVE-2026-42923 is a medium vulnerability published on May 20, 2026. NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the…
When was CVE-2026-42923 disclosed?
CVE-2026-42923 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-2026-42923 actively exploited?
CVE-2026-42923 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 73.6% of all scored CVEs.
What is the CVSS score of CVE-2026-42923?
CVE-2026-42923 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-42923?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42923, 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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