CVE-2026-50251

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

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, ghsa, secondary
Trending — 4 sources updated this week
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: None knownExposed: 0

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
5.3(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: Track

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%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
17%
KEV
Not listed

Published

July 22, 2026

Last Modified

July 24, 2026

Advisory Details (1)

Auto-updated Jul 22, 2026
No patch confirmed yet.
generic
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50251.txt

Vendor 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.

Patch Availability(1)

Vendor / EcosystemFixed in / 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

(5 across 5 ecosystems)
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
unbound—1.25.2-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
unbound1.13.1-1 ... 1.25.2-1 (47 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
unbound1.17.1-2 ... 1.26.0-2 (25 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
unbound1.22.0-2 ... 1.26.0-2 (15 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
unbound1.22.0-2 ... 1.25.1-1 (9 versions)1.25.2-1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 19× in last 7d / 89× 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 183 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-50251?
CVE-2026-50251 is a medium vulnerability 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 disclosed?
CVE-2026-50251 was first published in the National Vulnerability Database on July 22, 2026, with the most recent update on July 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-50251 actively exploited?
CVE-2026-50251 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 83.0% of all scored CVEs.
What is the CVSS score of CVE-2026-50251?
CVE-2026-50251 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-50251?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-50251, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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