CVE-2026-50251

MEDIUMPre-NVD 5.35.3
EchelonGraph scoreMEDIUM confidence

“—” 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.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source

Also known asEUVD-2026-47675 (ENISA EUVD) · GHSA-rj42-r8f9-w75j (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.

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.

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.
Exploitation0.2% × 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, 2026
Patch available.

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatunbound-main-1.25.2-0.1.hum12026-07-22redhat

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 1.25.2-r0: fixed in 1.25.2-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 ... 1.26.0-2 (15 versions)
  • every version up to 1.26.1-0+deb13u1: fixed in 1.26.1-0+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.22.0-2 ... 1.25.1-1 (9 versions)
  • every version up to 1.25.2-1: fixed in 1.25.2-1
—

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.

  1. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  2. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  3. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  4. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  5. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  6. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  7. 2026-10-25 14:22 UTCEG score recompute
  8. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  9. 2026-10-24 13:34 UTCEG score recompute
  10. 2026-10-24 13:34 UTCVendor advisory
  11. 2026-10-24 13:34 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  12. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  13. 2026-10-22 22:57 UTCEG score recompute
  14. 2026-10-22 22:56 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  15. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  16. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  17. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  18. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  19. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  20. 2026-10-18 03:33 UTCEG score recompute
  21. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  22. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  23. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  24. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  25. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
Show 75 more
  1. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  2. 2026-10-12 15:59 UTCEG score recompute
  3. 2026-10-11 19:42 UTCEG score recompute
  4. 2026-10-11 16:57 UTCEG score recompute
  5. 2026-10-11 14:21 UTCEG score recompute
  6. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  7. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  8. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  9. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  10. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  11. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  12. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  13. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  14. 2026-10-04 13:26 UTCEG score recompute
  15. 2026-10-04 13:26 UTCVendor advisory
  16. 2026-10-04 13:26 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  17. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  18. 2026-10-03 03:34 UTCEG score recompute
  19. 2026-10-03 03:34 UTCVendor advisory
  20. 2026-10-03 03:34 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  21. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  22. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  23. 2026-10-01 06:29 UTCEG score recompute
  24. 2026-10-01 06:29 UTCVendor advisory
  25. 2026-10-01 06:29 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  26. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  27. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  28. 2026-09-28 05:18 UTCEG score recompute
  29. 2026-09-28 05:18 UTCVendor advisory
  30. 2026-09-28 05:18 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  31. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  32. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  33. 2026-09-26 00:27 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  34. 2026-09-24 02:07 UTCEG score recompute
  35. 2026-09-24 02:07 UTCVendor advisory
  36. 2026-09-24 02:07 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  37. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  38. 2026-09-22 23:59 UTCEG score recompute
  39. 2026-09-22 23:59 UTCVendor advisory
  40. 2026-09-22 23:59 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  41. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  42. 2026-09-20 02:05 UTCEG score recompute
  43. 2026-09-20 02:05 UTCVendor advisory
  44. 2026-09-20 02:05 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  45. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  46. 2026-09-18 10:57 UTCEG score recompute
  47. 2026-09-18 10:57 UTCVendor advisory
  48. 2026-09-18 10:57 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  49. 2026-09-17 09:44 UTCEG score recompute
  50. 2026-09-17 09:44 UTCVendor advisory
  51. 2026-09-17 09:44 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  52. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  53. 2026-09-16 07:04 UTCEG score recompute
  54. 2026-09-16 07:04 UTCVendor advisory
  55. 2026-09-16 07:04 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  56. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  57. 2026-09-14 03:17 UTCEG score recompute
  58. 2026-09-14 03:17 UTCVendor advisory
  59. 2026-09-14 03:17 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  60. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  61. 2026-09-13 02:05 UTCEG score recompute
  62. 2026-09-13 02:05 UTCVendor advisory
  63. 2026-09-13 02:05 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  64. 2026-09-12 00:52 UTCEG score recompute
  65. 2026-09-12 00:52 UTCVendor advisory
  66. 2026-09-12 00:52 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  67. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  68. 2026-09-10 21:38 UTCEG score recompute
  69. 2026-09-10 21:38 UTCVendor advisory
  70. 2026-09-10 21:38 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  71. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  72. 2026-09-09 09:17 UTCEG score recompute
  73. 2026-09-09 09:17 UTCVendor advisory
  74. 2026-09-09 09:17 UTCGHSA enrichmentGHSA-rj42-r8f9-w75j · GitHub CVSS 5.3
  75. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 16th percentile

Frequently asked(5)

What is CVE-2026-50251?
CVE-2026-50251 is a medium-severity vulnerability; its CVE record was published on July 22, 2026. 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…
When was CVE-2026-50251 made public?
CVE-2026-50251 was made public on July 22, 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 July 22, 2026. EchelonGraph's copy of the record carries a last-modified date of October 24, 2026; the record at its source may have been updated since.
Is CVE-2026-50251 actively exploited?
CVE-2026-50251 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (16th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-50251?
CVE-2026-50251 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-50251?
A fix for CVE-2026-50251 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-50251 are linked in the Vendor Advisories panel on this page.

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