CVE-2026-42534

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
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 5.3Exploit: NoneExposed: 0

A fix is available — apply it.

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.

CVSS v3
5.3
EG Score
5.3(medium)
EPSS
40.4%
KEV
Not listed

Published

May 20, 2026

Last Modified

June 30, 2026

Advisory Details (1)

Auto-updated May 20, 2026
No patch confirmed yet.
generic
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42534.txt

Vendor Advisories for CVE-2026-42534(2)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuunbound-host (1.22.0-2ubuntu2.3) @ questing2026-06-29ubuntu

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

(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 9× in last 7d / 64× 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 134 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
  6. 2026-07-06 16:27 UTCEPSS rescore
  7. 2026-07-06 02:23 UTCEPSS rescore
  8. 2026-07-06 02:23 UTCEPSS rescore
  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. 2026-06-28 14:07 UTCEPSS rescore
  18. 2026-06-28 04:56 UTCEPSS rescore
  19. 2026-06-27 20:16 UTCEG score recompute
  20. 2026-06-27 20:16 UTCVendor advisory
  21. 2026-06-27 20:16 UTCGHSA enrichment
  22. 2026-06-27 03:08 UTCEPSS rescore
  23. 2026-06-26 19:35 UTCEG score recompute
  24. 2026-06-26 19:35 UTCVendor advisory
  25. 2026-06-26 19:35 UTCGHSA enrichment
Show 75 more
  1. 2026-06-25 16:15 UTCEG score recompute
  2. 2026-06-25 16:15 UTCVendor advisory
  3. 2026-06-25 16:14 UTCGHSA enrichment
  4. 2026-06-25 13:49 UTCEPSS rescore
  5. 2026-06-25 13:49 UTCEPSS rescore
  6. 2026-06-24 14:05 UTCEPSS rescore
  7. 2026-06-23 21:33 UTCEPSS rescore
  8. 2026-06-22 14:25 UTCEPSS rescore
  9. 2026-06-22 14:25 UTCEPSS rescore
  10. 2026-06-21 14:56 UTCEPSS rescore
  11. 2026-06-21 14:56 UTCEPSS rescore
  12. 2026-06-21 01:59 UTCEPSS rescore
  13. 2026-06-19 19:25 UTCEPSS rescore
  14. 2026-06-18 17:52 UTCEPSS rescore
  15. 2026-06-18 17:52 UTCEPSS rescore
  16. 2026-06-17 21:37 UTCEG score recompute
  17. 2026-06-17 21:37 UTCVendor advisory
  18. 2026-06-17 21:37 UTCGHSA enrichment
  19. 2026-06-17 17:53 UTCEPSS rescore
  20. 2026-06-16 22:16 UTCEG score recompute
  21. 2026-06-16 22:16 UTCVendor advisory
  22. 2026-06-16 22:16 UTCGHSA enrichment
  23. 2026-06-16 17:52 UTCEPSS rescore
  24. 2026-06-15 22:55 UTCEG score recompute
  25. 2026-06-15 22:55 UTCVendor advisory
  26. 2026-06-15 22:55 UTCGHSA enrichment
  27. 2026-06-15 17:49 UTCEPSS rescore
  28. 2026-06-14 21:50 UTCEG score recompute
  29. 2026-06-14 21:50 UTCVendor advisory
  30. 2026-06-14 21:50 UTCGHSA enrichment
  31. 2026-06-13 23:00 UTCEPSS rescore
  32. 2026-06-13 22:30 UTCEG score recompute
  33. 2026-06-13 22:30 UTCVendor advisory
  34. 2026-06-13 22:30 UTCGHSA enrichment
  35. 2026-06-12 23:12 UTCEPSS rescore
  36. 2026-06-12 23:12 UTCEPSS rescore
  37. 2026-06-12 19:33 UTCEG score recompute
  38. 2026-06-12 19:33 UTCVendor advisory
  39. 2026-06-12 19:33 UTCGHSA enrichment
  40. 2026-06-11 20:12 UTCEG score recompute
  41. 2026-06-11 20:12 UTCVendor advisory
  42. 2026-06-11 20:12 UTCGHSA enrichment
  43. 2026-06-11 14:00 UTCEPSS rescore
  44. 2026-06-10 22:18 UTCEPSS rescore
  45. 2026-06-10 20:52 UTCEG score recompute
  46. 2026-06-10 20:52 UTCVendor advisory
  47. 2026-06-10 20:52 UTCGHSA enrichment
  48. 2026-06-10 13:22 UTCEPSS rescore
  49. 2026-06-10 13:22 UTCEPSS rescore
  50. 2026-06-09 21:31 UTCEG score recompute
  51. 2026-06-09 21:31 UTCVendor advisory
  52. 2026-06-09 21:31 UTCGHSA enrichment
  53. 2026-06-08 21:41 UTCEG score recompute
  54. 2026-06-08 21:41 UTCVendor advisory
  55. 2026-06-08 21:41 UTCGHSA enrichment
  56. 2026-06-08 14:17 UTCEPSS rescore
  57. 2026-06-08 14:17 UTCEPSS rescore
  58. 2026-06-07 22:20 UTCEG score recompute
  59. 2026-06-07 22:20 UTCVendor advisory
  60. 2026-06-07 22:20 UTCGHSA enrichment
  61. 2026-06-07 15:25 UTCEPSS rescore
  62. 2026-06-07 15:25 UTCEPSS rescore
  63. 2026-06-06 23:00 UTCEG score recompute
  64. 2026-06-06 23:00 UTCVendor advisory
  65. 2026-06-06 23:00 UTCGHSA enrichment
  66. 2026-06-06 13:47 UTCEPSS rescore
  67. 2026-06-06 13:47 UTCEPSS rescore
  68. 2026-06-05 23:39 UTCEG score recompute
  69. 2026-06-05 23:39 UTCVendor advisory
  70. 2026-06-05 23:39 UTCGHSA enrichment
  71. 2026-06-05 22:47 UTCEPSS rescore
  72. 2026-06-05 06:10 UTCEPSS rescore
  73. 2026-06-05 06:10 UTCEPSS rescore
  74. 2026-06-05 00:19 UTCEG score recompute
  75. 2026-06-05 00:19 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-42534?
CVE-2026-42534 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 jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential…
When was CVE-2026-42534 disclosed?
CVE-2026-42534 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-2026-42534 actively exploited?
CVE-2026-42534 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 40.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42534?
CVE-2026-42534 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-42534?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42534, 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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