CVE-2026-56820

CRITICALNVD 9.19.1
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This critical-severity CVE scores 9.1 under NVD CVSS v3. EPSS exploit probability: 0.3% (24th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Trending — 3 sources updated this weekElevated

Also known asEUVD-2026-47582 (ENISA EUVD) · GHSA-272m-gcwp-mpwg (GitHub Security Advisories)Source: ENISA EUVD

9.1EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 9.1Exploit: No code on recordExposed services: Not assessed

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
9.1CRITICALmedium confidence
EG Risk
57
EG Risk 57/100

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)
Severity91% × 45%
Impact severity (EG Severity): CVSS 9.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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
24th
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 (9.1): severity, escalated by confirmed exploitation. This CVE's 9.1 is its impact severity (EG Severity), not escalated.

EG Severity
9.1 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-30). 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, Track* at medium and Attend at high mission impact.CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade 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, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (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 21, 2026

Last Modified

July 30, 2026

Advisory Details (5)

Auto-updated Sep 16, 2026
Patch available. Sources: github, github_commit, github_release.
GitHub advisoryMentions a patch (unverified)

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(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
redhatnetty-handler-ssl-ocsp2026-09-21redhat

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 rangeFix by version rangeDependents
netty1:4.1.48-10 ... 1:4.1.48-9 (16 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
netty1:4.1.48-10 ... 1:4.1.48-9 (12 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
netty1:4.1.48-10 ... 1:4.1.48-16 (8 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
netty1:4.1.48-10 ... 1:4.1.48-16 (7 versions)
  • every version on: no fix on record
—
Maven(1)
PackageVulnerable rangeFix by version rangeDependents
io.netty:netty-handler-ssl-ocsp4.1.100.Final ... 4.1.99.Final (50 versions)
  • 4.2.0.Final up to 4.2.16.Final: fixed in 4.2.16.Final
  • every version up to 4.1.136.Final: fixed in 4.1.136.Final
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 23× in last 7d / 80× 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 346 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 246 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-31 11:24 UTCEG score recompute
  2. 2026-10-31 11:24 UTCVendor advisory
  3. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  4. 2026-10-30 13:09 UTCEG score recompute
  5. 2026-10-30 13:09 UTCVendor advisory
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  7. 2026-10-29 14:54 UTCVendor advisory
  8. 2026-10-28 16:40 UTCEG score recompute
  9. 2026-10-28 16:40 UTCVendor advisory
  10. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  11. 2026-10-27 18:24 UTCEG score recompute
  12. 2026-10-27 18:24 UTCVendor advisory
  13. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  14. 2026-10-26 20:10 UTCEG score recompute
  15. 2026-10-26 20:10 UTCVendor advisory
  16. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  17. 2026-10-25 19:57 UTCEG score recompute
  18. 2026-10-25 19:57 UTCVendor advisory
  19. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  20. 2026-10-25 14:17 UTCEG score recompute
  21. 2026-10-24 21:42 UTCEG score recompute
  22. 2026-10-24 21:42 UTCVendor advisory
  23. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  24. 2026-10-23 23:26 UTCEG score recompute
  25. 2026-10-23 23:26 UTCVendor advisory
Show 75 more
  1. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  2. 2026-10-23 01:02 UTCEG score recompute
  3. 2026-10-23 01:02 UTCVendor advisory
  4. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  5. 2026-10-22 02:18 UTCEG score recompute
  6. 2026-10-22 02:18 UTCVendor advisory
  7. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  8. 2026-10-21 03:52 UTCEG score recompute
  9. 2026-10-21 03:52 UTCVendor advisory
  10. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  11. 2026-10-20 05:38 UTCEG score recompute
  12. 2026-10-20 05:38 UTCVendor advisory
  13. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  14. 2026-10-19 07:22 UTCEG score recompute
  15. 2026-10-19 07:22 UTCVendor advisory
  16. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  17. 2026-10-18 09:05 UTCVendor advisory
  18. 2026-10-18 03:29 UTCEG score recompute
  19. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  20. 2026-10-17 10:49 UTCEG score recompute
  21. 2026-10-17 10:49 UTCVendor advisory
  22. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  23. 2026-10-16 12:25 UTCEG score recompute
  24. 2026-10-16 12:25 UTCVendor advisory
  25. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  26. 2026-10-15 14:08 UTCEG score recompute
  27. 2026-10-15 14:08 UTCVendor advisory
  28. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  29. 2026-10-14 08:53 UTCEG score recompute
  30. 2026-10-14 08:53 UTCVendor advisory
  31. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  32. 2026-10-13 05:04 UTCEG score recompute
  33. 2026-10-13 05:04 UTCVendor advisory
  34. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  35. 2026-10-12 15:54 UTCEG score recompute
  36. 2026-10-12 06:49 UTCVendor advisory
  37. 2026-10-11 19:38 UTCEG score recompute
  38. 2026-10-11 16:53 UTCEG score recompute
  39. 2026-10-11 14:15 UTCEG score recompute
  40. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  41. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  42. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  43. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  44. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  45. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  46. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  47. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  48. 2026-10-04 13:29 UTCEG score recompute
  49. 2026-10-04 13:29 UTCVendor advisory
  50. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  51. 2026-10-03 03:36 UTCEG score recompute
  52. 2026-10-03 03:36 UTCVendor advisory
  53. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  54. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  55. 2026-10-01 15:12 UTCVendor advisory
  56. 2026-10-01 10:59 UTCVendor advisory
  57. 2026-10-01 06:31 UTCEG score recompute
  58. 2026-10-01 06:31 UTCVendor advisory
  59. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  60. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  61. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  62. 2026-09-28 09:34 UTCVendor advisory
  63. 2026-09-28 05:21 UTCEG score recompute
  64. 2026-09-28 05:21 UTCVendor advisory
  65. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  66. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  67. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  68. 2026-09-24 11:07 UTCVendor advisory
  69. 2026-09-24 06:54 UTCVendor advisory
  70. 2026-09-24 02:40 UTCVendor advisory
  71. 2026-09-23 22:27 UTCEG score recompute
  72. 2026-09-23 22:27 UTCVendor advisory
  73. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  74. 2026-09-23 08:30 UTCVendor advisory
  75. 2026-09-23 04:17 UTCVendor advisory

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-56820?
CVE-2026-56820 is a critical-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-56820 published?
The CVE record for CVE-2026-56820 was published on July 21, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of July 30, 2026; the record at its source may have been updated since.
Is CVE-2026-56820 actively exploited?
CVE-2026-56820 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (24th percentile of EPSS-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?
A fix for CVE-2026-56820 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-56820 are linked in the Vendor Advisories panel on this page.

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