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). GitHub Security Advisory CVSS 7.4 is lower than this score; a lower GitHub score revises it only when its advisory is newer than the CVE record's last change, and this advisory (published 2026-07-22) is not newer than that change (2026-07-30), so it does not.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Elevated

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 2026-11-12). 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, and whom BOD 26-04 binds: 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.

The score's inputs: 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

Patch Availability(3)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatnetty-handler-ssl-ocsp2026-09-21redhat
mavenio.netty:netty-handler-ssl-ocsp @ 4.1.136.Final (fixes < 4.1.136.Final)—ghsa
mavenio.netty:netty-handler-ssl-ocsp @ 4.2.16.Final (fixes >= 4.2.0.Final, < 4.2.16.Final)—ghsa

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 22× in last 7d / 77× 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 its CVE.org record (CNA or CISA ADP). 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 402 rows 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 302 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 16:53 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  2. 2026-11-13 10:59 UTCEchelonGraph re-scored
  3. 2026-11-13 10:59 UTCVendor advisory
  4. 2026-11-13 10:59 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  5. 2026-11-12 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  6. 2026-11-12 12:44 UTCEchelonGraph re-scored
  7. 2026-11-12 12:44 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  8. 2026-11-11 16:40 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  9. 2026-11-11 14:29 UTCEchelonGraph re-scored
  10. 2026-11-11 14:29 UTCVendor advisory
  11. 2026-11-11 14:29 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  12. 2026-11-10 16:44 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  13. 2026-11-10 16:15 UTCVendor advisory
  14. 2026-11-10 16:15 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  15. 2026-11-09 17:54 UTCEchelonGraph re-scored
  16. 2026-11-09 17:54 UTCVendor advisory
  17. 2026-11-09 17:54 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  18. 2026-11-09 16:35 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  19. 2026-11-08 19:40 UTCEchelonGraph re-scored
  20. 2026-11-08 19:40 UTCVendor advisory
  21. 2026-11-08 19:40 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  22. 2026-11-08 16:40 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  23. 2026-11-07 21:26 UTCEchelonGraph re-scored
  24. 2026-11-07 21:26 UTCVendor advisory
  25. 2026-11-07 21:26 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
Show 75 more
  1. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  2. 2026-11-06 23:10 UTCEchelonGraph re-scored
  3. 2026-11-06 23:10 UTCVendor advisory
  4. 2026-11-06 23:10 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  5. 2026-11-06 16:38 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  6. 2026-11-06 12:55 UTCOSV refresh
  7. 2026-11-06 00:56 UTCEchelonGraph re-scored
  8. 2026-11-06 00:56 UTCVendor advisory
  9. 2026-11-06 00:56 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  10. 2026-11-05 16:38 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  11. 2026-11-05 02:42 UTCEchelonGraph re-scored
  12. 2026-11-05 02:42 UTCVendor advisory
  13. 2026-11-05 02:42 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  14. 2026-11-04 16:36 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  15. 2026-11-04 04:27 UTCEchelonGraph re-scored
  16. 2026-11-04 04:27 UTCVendor advisory
  17. 2026-11-04 04:27 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  18. 2026-11-03 16:48 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  19. 2026-11-03 06:13 UTCEchelonGraph re-scored
  20. 2026-11-03 06:13 UTCVendor advisory
  21. 2026-11-03 06:12 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  22. 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  23. 2026-11-02 07:54 UTCEchelonGraph re-scored
  24. 2026-11-02 07:54 UTCVendor advisory
  25. 2026-11-02 07:54 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  26. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  27. 2026-11-01 09:39 UTCVendor advisory
  28. 2026-11-01 09:39 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  29. 2026-11-01 07:42 UTCGHSA enrichmentGHSA-272m-gcwp-mpwg · GitHub severity HIGH · GitHub CVSS 7.4
  30. 2026-11-01 07:42 UTCEchelonGraph re-scored
  31. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  32. 2026-10-31 11:24 UTCEchelonGraph re-scored
  33. 2026-10-31 11:24 UTCVendor advisory
  34. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  35. 2026-10-30 13:09 UTCEchelonGraph re-scored
  36. 2026-10-30 13:09 UTCVendor advisory
  37. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  38. 2026-10-29 14:54 UTCVendor advisory
  39. 2026-10-28 16:40 UTCEchelonGraph re-scored
  40. 2026-10-28 16:40 UTCVendor advisory
  41. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  42. 2026-10-27 18:24 UTCEchelonGraph re-scored
  43. 2026-10-27 18:24 UTCVendor advisory
  44. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  45. 2026-10-26 20:10 UTCEchelonGraph re-scored
  46. 2026-10-26 20:10 UTCVendor advisory
  47. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  48. 2026-10-25 19:57 UTCEchelonGraph re-scored
  49. 2026-10-25 19:57 UTCVendor advisory
  50. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  51. 2026-10-25 14:17 UTCEchelonGraph re-scored
  52. 2026-10-24 21:42 UTCEchelonGraph re-scored
  53. 2026-10-24 21:42 UTCVendor advisory
  54. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  55. 2026-10-23 23:26 UTCEchelonGraph re-scored
  56. 2026-10-23 23:26 UTCVendor advisory
  57. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  58. 2026-10-23 01:02 UTCEchelonGraph re-scored
  59. 2026-10-23 01:02 UTCVendor advisory
  60. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  61. 2026-10-22 02:18 UTCEchelonGraph re-scored
  62. 2026-10-22 02:18 UTCVendor advisory
  63. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  64. 2026-10-21 03:52 UTCEchelonGraph re-scored
  65. 2026-10-21 03:52 UTCVendor advisory
  66. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  67. 2026-10-20 05:38 UTCEchelonGraph re-scored
  68. 2026-10-20 05:38 UTCVendor advisory
  69. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  70. 2026-10-19 07:22 UTCEchelonGraph re-scored
  71. 2026-10-19 07:22 UTCVendor advisory
  72. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  73. 2026-10-18 09:05 UTCVendor advisory
  74. 2026-10-18 03:29 UTCEchelonGraph re-scored
  75. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile

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.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-56820

Explore →

Is Your Infrastructure Affected by CVE-2026-56820?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.