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
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 5.3Exploit: None knownExposed services: Not assessed

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
5.3MEDIUMmedium confidence
EG Risk
39
EG Risk 39/100

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%
EPSS PROB
0.4%
EPSS %ILE
32nd
KEV
Not listed

Published

May 20, 2026

Last Modified

July 24, 2026

Advisory Details (1)

Auto-updated May 20, 2026
Patch available.
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 / EcosystemFix (by version range) / PatchReleasedSource
ubuntuunbound-host (1.13.1-1ubuntu5.15) @ jammy2026-08-23ubuntu
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.

Affected Packages

(7 across 7 ecosystems)
Alpine:v3.22(1)
PackageVulnerable rangeFix by version rangeDependents
unbound—
  • 1.19.1 up to 1.25.2-r0: fixed in 1.25.2-r0
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
unbound—
  • 1.19.1 up to 1.25.2-r0: fixed in 1.25.2-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
unbound—
  • 1.19.1 up to 1.25.1-r0: fixed in 1.25.1-r0
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.13.1-1 ... 1.25.2-1 (47 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.17.1-2 ... 1.26.1-1 (26 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.22.0-2, 1.22.0-2+deb13u1, 1.22.0-2+deb13u2
  • every version up to 1.22.0-2+deb13u3: fixed in 1.22.0-2+deb13u3
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.22.0-2 ... 1.25.0-1 (8 versions)
  • every version up to 1.25.1-1: fixed in 1.25.1-1
—

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 7× in last 7d / 24× 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 239 total refreshes for this CVE.

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

Related CVEs(same product + same vendor + same CWE)

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 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 0.4% probability of exploitation in the next 30 days (32nd percentile of EPSS-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?
A fix for CVE-2026-42923 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-42923 are linked in the Vendor Advisories panel on this page.

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