CVE-2026-78227

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-09-16. A secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

NLnet Labs Unbound 1.22.0 up to and including 1.26.1, has a use-after-free vulnerability when compiled for DNS-over-QUIC support with '--with-libngtcp2'. Each DoQ stream owns an output buffer that holds the DNS response. ngtcp2's retransmission buffer keeps a shallow pointer into the output buffer for as long as a STREAM frame may be resent. On a client RESET_STREAM, the output buffer is freed but ngtcp2 still holds the matching retransmission entries. The next PTO timeout makes ngtcp2 re-encode the STREAM frame and copy from the freed buffer. A malicious actor that can query Unbound over DoQ and that withholds ACKs, sends RESET_STREAM, and waits for PTO, reaches this use-after-free with no privilege. This leads to retransmissions against freed memory and eventually an abnormal server exit under a 20-query spray.

CVSS v3
6.5
EG Score
6.5MEDIUMhigh confidence
EG Risk
29
EG Risk 29/100CISA SSVC

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
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
25th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 16, 2026

Last Modified

September 23, 2026

Advisory Details (1)

Auto-updated Sep 16, 2026
Patch available.
generic
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-78227.txt

Vendor Advisories for CVE-2026-78227(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 / EcosystemFix (by version range) / PatchReleasedSource
redhatunbound-main-1.26.1-1.hum12026-09-17redhat

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

(3 across 3 ecosystems)
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 ... 1.26.0-2 (12 versions)
  • every version up to 1.26.1-1: fixed in 1.26.1-1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 28× in last 7d / 81× 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.

  1. 2026-10-05 01:08 UTCEG score recompute
  2. 2026-10-05 01:08 UTCVendor advisory
  3. 2026-10-05 01:08 UTCGHSA enrichment
  4. 2026-10-04 23:22 UTCEPSS rescore
  5. 2026-10-04 02:44 UTCEG score recompute
  6. 2026-10-04 02:44 UTCVendor advisory
  7. 2026-10-04 02:44 UTCGHSA enrichment
  8. 2026-10-03 14:26 UTCEPSS rescore
  9. 2026-10-03 04:21 UTCEG score recompute
  10. 2026-10-03 04:21 UTCVendor advisory
  11. 2026-10-03 04:21 UTCGHSA enrichment
  12. 2026-10-02 05:57 UTCEG score recompute
  13. 2026-10-02 05:57 UTCVendor advisory
  14. 2026-10-02 05:57 UTCGHSA enrichment
  15. 2026-10-01 19:50 UTCEPSS rescore
  16. 2026-10-01 07:33 UTCEG score recompute
  17. 2026-10-01 07:33 UTCVendor advisory
  18. 2026-10-01 07:33 UTCGHSA enrichment
  19. 2026-09-30 09:10 UTCEG score recompute
  20. 2026-09-30 09:10 UTCVendor advisory
  21. 2026-09-30 09:10 UTCGHSA enrichment
  22. 2026-09-29 15:24 UTCEPSS rescore
  23. 2026-09-29 10:47 UTCEG score recompute
  24. 2026-09-29 10:47 UTCVendor advisory
  25. 2026-09-29 10:47 UTCGHSA enrichment
Show 56 more
  1. 2026-09-28 13:52 UTCEPSS rescore
  2. 2026-09-28 12:24 UTCVendor advisory
  3. 2026-09-28 12:24 UTCGHSA enrichment
  4. 2026-09-27 14:01 UTCEG score recompute
  5. 2026-09-27 14:01 UTCVendor advisory
  6. 2026-09-27 14:01 UTCGHSA enrichment
  7. 2026-09-27 13:48 UTCEPSS rescore
  8. 2026-09-26 15:59 UTCEPSS rescore
  9. 2026-09-26 15:34 UTCEG score recompute
  10. 2026-09-26 15:34 UTCVendor advisory
  11. 2026-09-26 15:34 UTCGHSA enrichment
  12. 2026-09-26 00:28 UTCEPSS rescore
  13. 2026-09-25 17:10 UTCVendor advisory
  14. 2026-09-25 17:10 UTCGHSA enrichment
  15. 2026-09-24 18:47 UTCEG score recompute
  16. 2026-09-24 18:47 UTCVendor advisory
  17. 2026-09-24 18:47 UTCGHSA enrichment
  18. 2026-09-24 14:04 UTCEPSS rescore
  19. 2026-09-23 20:24 UTCEG score recompute
  20. 2026-09-23 20:24 UTCVendor advisory
  21. 2026-09-23 20:24 UTCGHSA enrichment
  22. 2026-09-23 17:54 UTCEPSS rescore
  23. 2026-09-23 08:43 UTCEG score recompute
  24. 2026-09-23 08:43 UTCVendor advisory
  25. 2026-09-23 08:43 UTCGHSA enrichment
  26. 2026-09-22 16:01 UTCEPSS rescore
  27. 2026-09-22 10:20 UTCEG score recompute
  28. 2026-09-22 10:20 UTCVendor advisory
  29. 2026-09-22 10:19 UTCGHSA enrichment
  30. 2026-09-21 21:09 UTCEPSS rescore
  31. 2026-09-21 11:56 UTCEG score recompute
  32. 2026-09-21 11:56 UTCVendor advisory
  33. 2026-09-21 11:56 UTCGHSA enrichment
  34. 2026-09-20 20:16 UTCEPSS rescore
  35. 2026-09-20 13:32 UTCEG score recompute
  36. 2026-09-20 13:32 UTCVendor advisory
  37. 2026-09-20 13:32 UTCGHSA enrichment
  38. 2026-09-19 15:09 UTCEG score recompute
  39. 2026-09-19 15:09 UTCVendor advisory
  40. 2026-09-19 15:08 UTCGHSA enrichment
  41. 2026-09-18 19:28 UTCEPSS rescore
  42. 2026-09-18 16:45 UTCEG score recompute
  43. 2026-09-18 16:45 UTCVendor advisory
  44. 2026-09-18 16:45 UTCGHSA enrichment
  45. 2026-09-17 18:21 UTCVendor advisory
  46. 2026-09-17 18:20 UTCGHSA enrichment
  47. 2026-09-16 19:45 UTCGHSA enrichment
  48. 2026-09-16 16:35 UTCEG score recompute
  49. 2026-09-16 16:35 UTCGHSA enrichment
  50. 2026-09-16 15:45 UTCEG score recompute
  51. 2026-09-16 15:45 UTCGHSA enrichment
  52. 2026-09-16 14:08 UTCEPSS rescore
  53. 2026-09-16 09:31 UTCEG score recompute
  54. 2026-09-16 09:31 UTCGHSA enrichment
  55. 2026-09-16 08:42 UTCEG score recompute
  56. 2026-09-16 08:41 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-78227?
CVE-2026-78227 is a medium vulnerability published on September 16, 2026. NLnet Labs Unbound 1.22.0 up to and including 1.26.1, has a use-after-free vulnerability when compiled for DNS-over-QUIC support with '--with-libngtcp2'. Each DoQ stream owns an output buffer that holds the DNS response. ngtcp2's retransmission buffer keeps a shallow pointer into the output buffer…
When was CVE-2026-78227 disclosed?
CVE-2026-78227 was first published on September 16, 2026, with the most recent update on September 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-78227 actively exploited?
CVE-2026-78227 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (25th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-78227?
CVE-2026-78227 has a CVSS base score of 6.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-78227?
A fix for CVE-2026-78227 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-78227 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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