CVE-2026-42923

MEDIUMNVD 5.35.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

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, GitHub Security Advisory, NVD CVSS v3

Also known asEUVD-2026-31081 (ENISA EUVD) · GHSA-8f6w-8h24-fw66 (GitHub Security Advisories)Source: ENISA EUVD

5.3EG
EchelonGraph verdictMonitorRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%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 impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity53% × 45%
Impact severity (EG Severity): CVSS 5.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
27th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.3): severity, escalated by confirmed exploitation. This CVE's 5.3 is its impact severity (EG Severity), not escalated.

EG Severity
5.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

May 20, 2026

Last Modified

July 24, 2026

Advisory Details (1)

Auto-updated May 20, 2026
Patch available.

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntuunbound-host (1.22.0-2ubuntu2.3) @ questing2026-10-23ubuntu
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 8× in last 7d / 40× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 273 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 173 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  2. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  3. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  4. 2026-10-30 17:25 UTCOSV refresh
  5. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  7. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  9. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  11. 2026-10-25 14:28 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  13. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  14. 2026-10-23 02:03 UTCEG score recompute
  15. 2026-10-23 02:03 UTCVendor advisory
  16. 2026-10-23 02:03 UTCGHSA enrichmentGHSA-8f6w-8h24-fw66 · GitHub CVSS 5.3
  17. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  18. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  19. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  20. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  21. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  22. 2026-10-18 03:40 UTCEG score recompute
  23. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  24. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  25. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
Show 75 more
  1. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  2. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  3. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  4. 2026-10-12 16:06 UTCEG score recompute
  5. 2026-10-11 19:48 UTCEG score recompute
  6. 2026-10-11 17:03 UTCEG score recompute
  7. 2026-10-11 14:29 UTCEG score recompute
  8. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  9. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  10. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  11. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  12. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  13. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  14. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  15. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  16. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  17. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  18. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  19. 2026-09-30 03:10 UTCOSV refresh
  20. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  21. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  22. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  23. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  24. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  25. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  26. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  27. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  28. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  29. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  30. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  31. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  32. 2026-09-11 05:23 UTCOSV refresh
  33. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  34. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  35. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  36. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  37. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  38. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  39. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  40. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  41. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  42. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  43. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  44. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  45. 2026-08-23 16:57 UTCEG score recompute
  46. 2026-08-23 16:57 UTCVendor advisory
  47. 2026-08-23 16:57 UTCGHSA enrichmentGHSA-8f6w-8h24-fw66 · GitHub CVSS 5.3
  48. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  49. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  50. 2026-08-21 22:55 UTCEG score recompute
  51. 2026-08-21 22:55 UTCVendor advisory
  52. 2026-08-21 22:55 UTCGHSA enrichmentGHSA-8f6w-8h24-fw66 · GitHub CVSS 5.3
  53. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  54. 2026-08-20 18:56 UTCEG score recompute
  55. 2026-08-20 18:56 UTCVendor advisory
  56. 2026-08-20 18:56 UTCGHSA enrichmentGHSA-8f6w-8h24-fw66 · GitHub CVSS 5.3
  57. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  58. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  59. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  60. 2026-08-17 09:54 UTCEG score recompute
  61. 2026-08-17 09:54 UTCVendor advisory
  62. 2026-08-17 09:54 UTCGHSA enrichmentGHSA-8f6w-8h24-fw66 · GitHub CVSS 5.3
  63. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  64. 2026-08-16 03:30 UTCEG score recompute
  65. 2026-08-16 03:30 UTCVendor advisory
  66. 2026-08-16 03:30 UTCGHSA enrichmentGHSA-8f6w-8h24-fw66 · GitHub CVSS 5.3
  67. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  68. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  69. 2026-08-14 02:02 UTCEG score recompute
  70. 2026-08-14 02:02 UTCVendor advisory
  71. 2026-08-14 02:02 UTCGHSA enrichmentGHSA-8f6w-8h24-fw66 · GitHub CVSS 5.3
  72. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  73. 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  74. 2026-08-12 11:57 UTCEG score recompute
  75. 2026-08-12 11:57 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-42923?
CVE-2026-42923 is a medium-severity vulnerability; its CVE record was 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 made public?
CVE-2026-42923 was made public on May 20, 2026: that is the date its CVE record's CNA, NLnet Labs, gives for when the vulnerability was made public. The CVE record itself was published on May 20, 2026. EchelonGraph's copy of the record carries a last-modified date of July 24, 2026; the record at its source may have been updated since.
Is CVE-2026-42923 actively exploited?
CVE-2026-42923 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (27th 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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