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
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.7%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 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
5.3MEDIUMmedium 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%
Exploitation1% × 40%
Automatability100% × 15%
EPSS PROB
0.7%
EPSS %ILE
52nd
KEV
Not listed

Published

May 20, 2026

Last Modified

September 1, 2026

Advisory Details (1)

Auto-updated May 20, 2026
Patch available.
generic
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42534.txt

Vendor Advisories for CVE-2026-42534(6)

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

Patch Availability(5)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntuunbound-host (1.24.2-1ubuntu2.1) @ resolute2026-08-25ubuntu
redhatunbound-0:1.16.2-5.12.el8_102026-07-09redhat
redhatunbound-0:1.24.2-3.el9_8.22026-07-08redhat
redhatunbound-0:1.24.2-7.el10_2.22026-07-07redhat
redhatunbound-main-1.25.1-2.hum12026-06-07redhat

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—
  • every version up to 1.25.2-r0: fixed in 1.25.2-r0
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
unbound—
  • every version up to 1.25.2-r0: fixed in 1.25.2-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
unbound—
  • every version 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(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 8× 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 267 total refreshes for this CVE.

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

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

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 on May 20, 2026, with the most recent update on September 1, 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 0.7% probability of exploitation in the next 30 days (52nd percentile of EPSS-scored CVEs).
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?
A fix for CVE-2026-42534 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-42534 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-42534

Explore →

Is Your Infrastructure Affected by CVE-2026-42534?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Book a Demo →Browse All CVEs