CVE-2026-75596

HIGHNVD 7.57.5
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.4% (31st 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

Also known asEUVD-2026-63092 (ENISA EUVD) · GHSA-fccg-mwvh-qqg4 (GitHub Security Advisories)Source: ENISA EUVD

7.5EG
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).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Final and 4.2.17.Final, the default io.netty.handler.ssl.SniHandler constructors use the pre-handshake ClientHello aggregation path in handler/src/main/java/io/netty/handler/ssl/SslClientHelloHandler.java at io.netty.handler.ssl.SslClientHelloHandler#decode, where handshakeBuffer.clear() and writeBytes() recopy all previously received body bytes for every additional TLS record. An unauthenticated remote peer can advertise a large ClientHello and deliver its body in thousands of tiny records, causing quadratic CPU work on the event loop before the TLS handshake completes and degrading TLS handling for other clients. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
49
EG Risk 49/100

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)
Severity75% × 45%
Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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
0.4%
EPSS %ILE
31st
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 (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.

EG Severity
7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-10). 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 or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days 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 or medium mission impact; Attend at high (mission-essential systems).

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

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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

August 19, 2026

Last Modified

October 26, 2026

Advisory Details (7)

Auto-updated Aug 19, 2026
Patch available. Sources: github, github_pr, github_commit, github_release.
GitHub release Patch Available

netty-4.2.17.Final

Patch available: netty/netty netty-4.2.17.Final

https://github.com/netty/netty/releases/tag/netty-4.2.17.Final
GitHub release Patch Available

netty-4.1.137.Final

Patch available: netty/netty netty-4.1.137.Final

https://github.com/netty/netty/releases/tag/netty-4.1.137.Final
GitHub commit Patch Available

commit 9e0519239108 (netty/netty)

Patch available: netty/netty netty-4.1.137.Final (contains commit 9e0519239108)

https://github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961
GitHub commit Patch Available

commit 1b5abc6443b6 (netty/netty)

Patch available: netty/netty netty-4.2.17.Final (contains commit 1b5abc6443b6)

https://github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7
GitHub pull request Patch Available

Merge changes from forks (#17213)

Patch available: netty/netty netty-4.1.137.Final (PR #17217 merged 2026-08-06)

https://github.com/netty/netty/pull/17217
GitHub pull request Patch Available

Merge changes from forks

Patch available: netty/netty netty-4.2.17.Final (PR #17213 merged 2026-08-04)

https://github.com/netty/netty/pull/17213
GitHub advisoryMentions a patch (unverified)

Fragmented ClientHello records trigger quadratic pre-handshake reassembly in default SNI parsing · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-fccg-mwvh-qqg4

Vendor Advisories for CVE-2026-75596(1)

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

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
mavenio.netty:netty-handler @ 4.2.17.Final (fixes >= 4.2.0.Final, <= 4.2.16.Final)—ghsa
mavenio.netty:netty-handler @ 4.1.137.Final (fixes <= 4.1.136.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

(4 across 4 ecosystems)
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-handler4.0.0.Alpha1 ... 4.1.99.Final (230 versions)
  • 4.2.0.Final up to 4.2.17.Final: fixed in 4.2.17.Final
  • every version up to 4.1.137.Final: fixed in 4.1.137.Final
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 33× 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 145 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 45 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-12 16:34 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  2. 2026-11-11 16:40 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  3. 2026-11-11 05:13 UTCEchelonGraph re-scored
  4. 2026-11-11 05:12 UTCGHSA enrichmentGHSA-fccg-mwvh-qqg4 · GitHub severity MODERATE
  5. 2026-11-10 16:45 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  6. 2026-11-09 16:36 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  7. 2026-11-08 16:40 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  8. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  9. 2026-11-06 16:39 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  10. 2026-11-05 16:38 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  11. 2026-11-04 16:36 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  12. 2026-11-04 00:47 UTCEchelonGraph re-scored
  13. 2026-11-04 00:47 UTCGHSA enrichmentGHSA-fccg-mwvh-qqg4 · GitHub severity MODERATE
  14. 2026-11-03 16:49 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  15. 2026-11-02 16:46 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  16. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  17. 2026-11-01 07:39 UTCGHSA enrichmentGHSA-fccg-mwvh-qqg4 · GitHub severity MODERATE
  18. 2026-11-01 07:39 UTCEchelonGraph re-scored
  19. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  20. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  21. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  22. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  23. 2026-10-27 21:09 UTCEchelonGraph re-scored
  24. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  25. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
Show 75 more
  1. 2026-10-26 10:26 UTCEchelonGraph re-scored
  2. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  3. 2026-10-25 14:02 UTCEchelonGraph re-scored
  4. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  5. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  6. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  7. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  8. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  9. 2026-10-20 11:00 UTCEchelonGraph re-scored
  10. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  11. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  12. 2026-10-18 03:13 UTCEchelonGraph re-scored
  13. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  14. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  15. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  16. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  17. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  18. 2026-10-13 07:20 UTCEchelonGraph re-scored
  19. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  20. 2026-10-12 15:39 UTCEchelonGraph re-scored
  21. 2026-10-11 19:24 UTCEchelonGraph re-scored
  22. 2026-10-11 16:40 UTCEchelonGraph re-scored
  23. 2026-10-11 13:59 UTCEchelonGraph re-scored
  24. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  25. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  26. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  27. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  28. 2026-10-08 06:16 UTCEchelonGraph re-scored
  29. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  30. 2026-10-06 19:31 UTCEchelonGraph re-scored
  31. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  32. 2026-10-06 07:54 UTCEchelonGraph re-scored
  33. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  34. 2026-10-05 05:07 UTCEchelonGraph re-scored
  35. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  36. 2026-10-03 16:53 UTCEchelonGraph re-scored
  37. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  38. 2026-10-02 22:00 UTCEchelonGraph re-scored
  39. 2026-10-01 22:45 UTCEchelonGraph re-scored
  40. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  41. 2026-09-30 20:33 UTCEchelonGraph re-scored
  42. 2026-09-30 08:35 UTCEchelonGraph re-scored
  43. 2026-09-29 15:24 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  44. 2026-09-28 21:41 UTCEchelonGraph re-scored
  45. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  46. 2026-09-27 16:08 UTCEchelonGraph re-scored
  47. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  48. 2026-09-27 04:22 UTCEchelonGraph re-scored
  49. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  50. 2026-09-26 00:28 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  51. 2026-09-24 19:31 UTCEchelonGraph re-scored
  52. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  53. 2026-09-23 20:07 UTCEchelonGraph re-scored
  54. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  55. 2026-09-22 19:33 UTCEchelonGraph re-scored▼ 1.20
  56. 2026-09-22 19:32 UTCNVD updateCVSS v3 → 7.5
  57. 2026-09-22 16:01 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  58. 2026-09-22 08:13 UTCEchelonGraph re-scored
  59. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  60. 2026-09-20 21:10 UTCEchelonGraph re-scored
  61. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  62. 2026-09-19 21:52 UTCEchelonGraph re-scored
  63. 2026-09-18 21:41 UTCEchelonGraph re-scored
  64. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  65. 2026-09-17 21:28 UTCEchelonGraph re-scored
  66. 2026-09-16 20:05 UTCEchelonGraph re-scored
  67. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  68. 2026-09-16 06:28 UTCEchelonGraph re-scored
  69. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  70. 2026-09-15 06:50 UTCEchelonGraph re-scored
  71. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  72. 2026-09-13 19:31 UTCEchelonGraph re-scored
  73. 2026-09-12 20:17 UTCEchelonGraph re-scored
  74. 2026-09-12 15:02 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  75. 2026-09-11 21:03 UTCEchelonGraph re-scored

Frequently asked(5)

What is CVE-2026-75596?
CVE-2026-75596 is a high-severity vulnerability; its CVE record was published on August 19, 2026. Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Final and 4.2.17.Final, the default io.netty.handler.ssl.SniHandler constructors use the pre-handshake ClientHello aggregation path in handler/src/main/java/io/netty/handler/ssl/SslClientHelloHandler.java at…
When was the CVE record for CVE-2026-75596 published?
The CVE record for CVE-2026-75596 was published on August 19, 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 October 26, 2026; the record at its source may have been updated since.
Is CVE-2026-75596 actively exploited?
CVE-2026-75596 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (31st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-75596?
CVE-2026-75596 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-75596?
A fix for CVE-2026-75596 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-75596 are linked in the Vendor Advisories panel on this page.

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