In NLnet Labs Unbound up to and including version 1.25.1, when 'unwanted-reply-threshold' is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured 'unwanted-reply-threshold' that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of 'unwanted-reply-threshold' to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over loopback), Unbound's own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and 127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The counter resets to zero on every cache flush, so the attack loops forever.
CVE-2026-50251
“—” beside the score: it is equal to the CVSS score beside it.
Score 5.3 from GitHub Security Advisory published 2026-07-22. A secondary CVSS source baseline 5.3; sources differ by 0.0.
Also known asEUVD-2026-47675 (ENISA EUVD) · GHSA-rj42-r8f9-w75j (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.Exploitation0.2% × 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
- 16th
- 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 (model v2026.06.15, score date 2026-10-24). 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: 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.
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
July 22, 2026
Last Modified
October 24, 2026
Advisory Details (1)
Auto-updated Jul 22, 2026Vendor Advisories for CVE-2026-50251(3)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- CVE-2026-50251Microsoft Security Response Center (MSRC)Medium
Attacker supplied '0.0.0.0'/'::' glue triggers defensive full-cache flush
- GHSA-rj42-r8f9-w75jGitHub Security AdvisoriesMedium
In NLnet Labs Unbound up to and including version 1.25.1, when 'unwanted-reply-threshold' is...
- RHSA-2026:43588Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
Patch Availability(1)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| redhat | unbound-main-1.25.2-0.1.hum1 | 2026-07-22 | 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 ... 1.26.0-2 (15 versions) |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.22.0-2 ... 1.25.1-1 (9 versions) |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 8× in last 7d / 47× 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 260 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 160 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-10-25 14:22 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-10-24 13:34 UTCEG score recompute
- 2026-10-24 13:34 UTCVendor advisory
- 2026-10-24 13:34 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-22 22:57 UTCEG score recompute
- 2026-10-22 22:56 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-18 03:33 UTCEG score recompute
- 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
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- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-12 15:59 UTCEG score recompute
- 2026-10-11 19:42 UTCEG score recompute
- 2026-10-11 16:57 UTCEG score recompute
- 2026-10-11 14:21 UTCEG score recompute
- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 15th percentile
- 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-04 13:26 UTCEG score recompute
- 2026-10-04 13:26 UTCVendor advisory
- 2026-10-04 13:26 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-03 03:34 UTCEG score recompute
- 2026-10-03 03:34 UTCVendor advisory
- 2026-10-03 03:34 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-01 06:29 UTCEG score recompute
- 2026-10-01 06:29 UTCVendor advisory
- 2026-10-01 06:29 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 31st percentile
- 2026-09-28 05:18 UTCEG score recompute
- 2026-09-28 05:18 UTCVendor advisory
- 2026-09-28 05:18 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 31st percentile
- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 31st percentile
- 2026-09-26 00:27 UTCEPSS rescoreEPSS 0.4% · 31st percentile
- 2026-09-24 02:07 UTCEG score recompute
- 2026-09-24 02:07 UTCVendor advisory
- 2026-09-24 02:07 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.3% · 17th percentile
- 2026-09-22 23:59 UTCEG score recompute
- 2026-09-22 23:59 UTCVendor advisory
- 2026-09-22 23:59 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 17th percentile
- 2026-09-20 02:05 UTCEG score recompute
- 2026-09-20 02:05 UTCVendor advisory
- 2026-09-20 02:05 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 17th percentile
- 2026-09-18 10:57 UTCEG score recompute
- 2026-09-18 10:57 UTCVendor advisory
- 2026-09-18 10:57 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-17 09:44 UTCEG score recompute
- 2026-09-17 09:44 UTCVendor advisory
- 2026-09-17 09:44 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 17th percentile
- 2026-09-16 07:04 UTCEG score recompute
- 2026-09-16 07:04 UTCVendor advisory
- 2026-09-16 07:04 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-09-14 03:17 UTCEG score recompute
- 2026-09-14 03:17 UTCVendor advisory
- 2026-09-14 03:17 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-09-13 02:05 UTCEG score recompute
- 2026-09-13 02:05 UTCVendor advisory
- 2026-09-13 02:05 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-12 00:52 UTCEG score recompute
- 2026-09-12 00:52 UTCVendor advisory
- 2026-09-12 00:52 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-09-10 21:38 UTCEG score recompute
- 2026-09-10 21:38 UTCVendor advisory
- 2026-09-10 21:38 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.3% · 16th percentile
- 2026-09-09 09:17 UTCEG score recompute
- 2026-09-09 09:17 UTCVendor advisory
- 2026-09-09 09:17 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
- 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 16th percentile
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownAlpine:v3.22:unbound
Same vendor
10 shownredhat:RHSA-2026:43588
Frequently asked(5)
What is CVE-2026-50251?
When was CVE-2026-50251 made public?
Is CVE-2026-50251 actively exploited?
What is the CVSS score of CVE-2026-50251?
How do I remediate CVE-2026-50251?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-50251
Is Your Infrastructure Affected by CVE-2026-50251?
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