CVE-2026-56820

CRITICALNVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 87% 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, nvd
Trending — 3 sources updated this weekElevated
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: Elevated riskExposed: 0

A fix is available — apply it.

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and prior to 4.1.135.Final, OcspClient does not validate that the CertificateID in an OCSP response matches the requested CertificateID, which can lead to replay attack. OcspClient.validateResponse accepts a legitimately signed GOOD status response for an unrelated certificate issued by the same CA, allowing bypass of revocation checks for another certificate. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
57(Track*)
EG Risk 57/100SSVC: 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
Severity91% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
13%
KEV
Not listed

Published

July 21, 2026

Last Modified

July 30, 2026

Advisory Details (5)

Auto-updated Sep 16, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_release.
github Patch Available🟡 PoC Available

Missing CertificateID Validation in OCSP Response Allows Replay Attacks · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-272m-gcwp-mpwg
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_release Patch Available

netty-4.1.136.Final

Patch available: netty/netty netty-4.1.136.Final

https://github.com/netty/netty/releases/tag/netty-4.1.136.Final
github_commit Patch Available

commit bb2ff68a1fb7 (netty/netty)

Patch available: netty/netty netty-4.1.136.Final (contains commit bb2ff68a1fb7)

https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6
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-2026-56820(2)

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
redhatnetty-handler-ssl-ocsp2026-08-13redhat

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)
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-handler-ssl-ocsp4.1.100.Final ... 4.1.99.Final (50 versions)4.1.136.Final—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 30× in last 7d / 147× 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 225 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-56820?
CVE-2026-56820 is a critical vulnerability published on July 21, 2026. Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and prior to 4.1.135.Final, OcspClient does not validate that the CertificateID in an OCSP response matches the requested CertificateID, which can lead to replay…
When was CVE-2026-56820 disclosed?
CVE-2026-56820 was first published in the National Vulnerability Database on July 21, 2026, with the most recent update on July 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56820 actively exploited?
CVE-2026-56820 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 87.4% of all scored CVEs.
What is the CVSS score of CVE-2026-56820?
CVE-2026-56820 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-56820?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56820, 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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