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.
CVE-2026-42534
“—” 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.
Also known asEUVD-2026-31082 (ENISA EUVD) · GHSA-xfcv-gp55-3wpf (GitHub Security Advisories)Source: ENISA EUVD
- Lower severity and no public exploit yet
A fix is available — apply it.
- CVSS v3
- 5.3
- EG Score
- 5.3MEDIUMmedium confidence
- EG Risk
- 39EG 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.Exploitation0.7% × 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
- 0.6%
- EPSS %ILE
- 48th
- 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
- 0.6% 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
September 1, 2026
Advisory Details (1)
Auto-updated May 20, 2026Vendor 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.
- RHSA-2026:37282Red Hat Product SecurityHigh
Red Hat Security Advisory: unbound security update
- RHSA-2026:36777Red Hat Product SecurityHigh
Red Hat Security Advisory: unbound security update
- RHSA-2026:36320Red Hat Product SecurityHigh
Red Hat Security Advisory: unbound security update
- RHSA-2026:24013Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
- CVE-2026-42534Microsoft Security Response Center (MSRC)Low
Jostle logic bypass degrades resolution performance
- GHSA-xfcv-gp55-3wpfGitHub Security AdvisoriesMedium
NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic...
Patch Availability(5)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| ubuntu | unbound-host (1.24.2-1ubuntu2.1) @ resolute | 2026-10-23 | ubuntu |
| redhat | unbound-0:1.16.2-5.12.el8_10 | 2026-07-09 | redhat |
| redhat | unbound-0:1.24.2-3.el9_8.2 | 2026-07-08 | redhat |
| redhat | unbound-0:1.24.2-7.el10_2.2 | 2026-07-07 | redhat |
| redhat | unbound-main-1.25.1-2.hum1 | 2026-06-07 | redhat |
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)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | — |
| — |
Alpine:v3.23(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | — |
| — |
Alpine:v3.24(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | — |
| — |
Debian:11(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.13.1-1 ... 1.25.2-1 (47 versions) |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.17.1-2 ... 1.26.1-1 (26 versions) |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.22.0-2, 1.22.0-2+deb13u1, 1.22.0-2+deb13u2 |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.22.0-2 ... 1.25.0-1 (8 versions) |
| — |
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 / 41× 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 301 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 201 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-30 17:25 UTCOSV refresh
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.6% · 48th percentile
- 2026-10-25 14:29 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.7% · 54th percentile
- 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
- 2026-10-23 02:06 UTCEG score recompute
- 2026-10-23 02:06 UTCVendor advisory
- 2026-10-23 02:05 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-18 03:41 UTCEG score recompute
- 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
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- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-12 16:07 UTCEG score recompute
- 2026-10-11 19:49 UTCEG score recompute
- 2026-10-11 17:03 UTCEG score recompute
- 2026-10-11 14:29 UTCEG score recompute
- 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-10 02:33 UTCOSV refresh
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.7% · 51st percentile
- 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.7% · 51st percentile
- 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-20 11:51 UTCOSV refresh
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-01 13:47 UTCVendor advisory
- 2026-09-01 13:47 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
- 2026-09-01 12:21 UTCEG score recompute
- 2026-09-01 12:21 UTCVendor advisory
- 2026-09-01 12:21 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
- 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-25 12:20 UTCEG score recompute
- 2026-08-25 12:20 UTCVendor advisory
- 2026-08-25 12:20 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
- 2026-08-23 16:57 UTCEG score recompute
- 2026-08-23 16:57 UTCVendor advisory
- 2026-08-23 16:57 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
- 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-21 22:55 UTCEG score recompute
- 2026-08-21 22:55 UTCVendor advisory
- 2026-08-21 22:55 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
- 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-20 18:56 UTCEG score recompute
- 2026-08-20 18:56 UTCVendor advisory
- 2026-08-20 18:56 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
- 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-17 09:54 UTCEG score recompute
- 2026-08-17 09:54 UTCVendor advisory
- 2026-08-17 09:54 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
- 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-08-16 03:30 UTCEG score recompute
- 2026-08-16 03:30 UTCVendor advisory
- 2026-08-16 03:30 UTCGHSA enrichmentGHSA-xfcv-gp55-3wpf · GitHub CVSS 5.3
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownAlpine:v3.22:unbound
Same vendor
10 shownredhat:RHSA-2026:24013 · redhat:RHSA-2026:36320 · ubuntu:USN-8282-1
Frequently asked(5)
What is CVE-2026-42534?
When was CVE-2026-42534 made public?
Is CVE-2026-42534 actively exploited?
What is the CVSS score of CVE-2026-42534?
How do I remediate CVE-2026-42534?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-42534
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