CVE-2026-56816

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 57% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Netty is a network application framework for development of protocol servers and clients. Prior to 4.2.16.Final, Netty's Http3FrameCodec buffers incoming data for HTTP/3 reserved frame types up to the wire-specified payload length without limits; decodeFrame trusts payLoadLength, allowing an attacker to open multiple QUIC streams and send reserved frames with very large payload lengths to cause memory exhaustion and denial of service. This issue is fixed in version 4.2.16.Final.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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
Severity75% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
43%
KEV
Not listed

Published

July 21, 2026

Last Modified

August 7, 2026

Advisory Details (3)

Auto-updated Jul 22, 2026
🔬 Proof of concept available. Patch available. Sources: github_release, github, github_commit.
github Patch Available🟡 PoC Available

Memory Exhaustion via HTTP/3 Reserved Frame Types · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-hpcc-26xq-25fv
github_release Patch Available

netty-4.2.16.Final

Patch available: netty/netty netty-4.2.16.Final

https://github.com/netty/netty/releases/tag/netty-4.2.16.Final
github_commit Patch Available

commit 5b68c61f37aa (netty/netty)

Patch available: netty/netty netty-4.2.16.Final (contains commit 5b68c61f37aa)

https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b

Vendor Advisories for CVE-2026-56816(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-9 (16 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-9 (12 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-16 (8 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-16 (7 versions)——
Maven(1)
PackageVulnerable rangeFixed inDependents
io.netty:netty-codec-http34.2.10.Final ... 4.2.9.Final (14 versions)4.2.16.Final—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 45× 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 102 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-56816?
CVE-2026-56816 is a high vulnerability published on July 21, 2026. Netty is a network application framework for development of protocol servers and clients. Prior to 4.2.16.Final, Netty's Http3FrameCodec buffers incoming data for HTTP/3 reserved frame types up to the wire-specified payload length without limits; decodeFrame trusts payLoadLength, allowing an…
When was CVE-2026-56816 disclosed?
CVE-2026-56816 was first published in the National Vulnerability Database on July 21, 2026, with the most recent update on August 7, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56816 actively exploited?
CVE-2026-56816 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 57.3% of all scored CVEs.
What is the CVSS score of CVE-2026-56816?
CVE-2026-56816 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-56816?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56816, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-56816

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