CVE-2026-75595

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 — 4 sources updated this week

Also known asEUVD-2026-63095 (ENISA EUVD) · GHSA-c4c3-7fpv-j4q5 (GitHub Security Advisories)Source: ENISA EUVD

9.1EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 9.1Exploit: 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.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause an IndexOutOfBoundsException and invoke select(ctx, null). This selects the default SslContext instead of the SNI-specific context. In deployments where per-SNI clientAuth=REQUIRE is the sole mutual TLS gate, the default SslContext uses clientAuth=NONE or clientAuth=OPTIONAL, and no application-layer certificate verification exists, an unauthenticated remote attacker can bypass the protected route's mutual TLS requirement. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
41
EG Risk 41/100

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.
Exploitation0.3% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (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.
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 2026-11-02). 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; Track* at high (mission-essential systems).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 or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (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

August 19, 2026

Last Modified

October 26, 2026

Advisory Details (7)

Auto-updated Sep 15, 2026
Patch available. Sources: github, github_commit, github_pr, github_release.
GitHub advisoryMentions a patch (unverified)

SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-c4c3-7fpv-j4q5
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 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 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

Vendor Advisories for CVE-2026-75595(3)

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

Patch Availability(3)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatnetty-handler2026-10-15redhat
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(2)

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

Data Freshness Timeline

(refreshed 25× in last 7d / 106× 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 229 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 129 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-03 16:49 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  2. 2026-11-03 14:43 UTCEG score recompute
  3. 2026-11-03 14:43 UTCVendor advisory
  4. 2026-11-03 14:43 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  5. 2026-11-02 16:46 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  6. 2026-11-02 14:14 UTCEG score recompute
  7. 2026-11-02 14:14 UTCVendor advisory
  8. 2026-11-02 14:14 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  9. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  10. 2026-11-01 14:07 UTCVendor advisory
  11. 2026-11-01 14:07 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  12. 2026-11-01 07:39 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  13. 2026-11-01 07:39 UTCEG score recompute
  14. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  15. 2026-10-31 13:57 UTCEG score recompute
  16. 2026-10-31 13:57 UTCVendor advisory
  17. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  18. 2026-10-30 13:50 UTCEG score recompute
  19. 2026-10-30 13:50 UTCVendor advisory
  20. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  21. 2026-10-29 13:39 UTCEG score recompute
  22. 2026-10-29 13:39 UTCVendor advisory
  23. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  24. 2026-10-28 13:29 UTCEG score recompute
  25. 2026-10-28 13:29 UTCVendor advisory
Show 75 more
  1. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  2. 2026-10-27 13:12 UTCVendor advisory
  3. 2026-10-27 10:35 UTCEG score recompute
  4. 2026-10-27 10:35 UTCVendor advisory
  5. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  6. 2026-10-26 10:26 UTCVendor advisory
  7. 2026-10-26 09:42 UTCEG score recompute
  8. 2026-10-26 09:42 UTCVendor advisory
  9. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  10. 2026-10-25 14:02 UTCEG score recompute
  11. 2026-10-25 09:34 UTCEG score recompute
  12. 2026-10-25 09:34 UTCVendor advisory
  13. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  14. 2026-10-24 09:26 UTCEG score recompute
  15. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  16. 2026-10-23 09:18 UTCEG score recompute
  17. 2026-10-23 09:18 UTCVendor advisory
  18. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  19. 2026-10-22 09:10 UTCEG score recompute
  20. 2026-10-22 09:10 UTCVendor advisory
  21. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  22. 2026-10-21 09:02 UTCEG score recompute
  23. 2026-10-21 09:02 UTCVendor advisory
  24. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  25. 2026-10-20 08:53 UTCEG score recompute
  26. 2026-10-20 08:53 UTCVendor advisory
  27. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  28. 2026-10-19 08:44 UTCEG score recompute
  29. 2026-10-19 08:44 UTCVendor advisory
  30. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  31. 2026-10-18 08:36 UTCVendor advisory
  32. 2026-10-18 03:13 UTCEG score recompute
  33. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  34. 2026-10-17 07:23 UTCEG score recompute
  35. 2026-10-17 07:23 UTCVendor advisory
  36. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  37. 2026-10-16 07:14 UTCEG score recompute
  38. 2026-10-16 07:14 UTCVendor advisory
  39. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  40. 2026-10-15 06:05 UTCEG score recompute
  41. 2026-10-15 06:05 UTCVendor advisory
  42. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  43. 2026-10-14 01:42 UTCEG score recompute
  44. 2026-10-14 01:42 UTCVendor advisory
  45. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  46. 2026-10-12 21:53 UTCEG score recompute
  47. 2026-10-12 21:53 UTCVendor advisory
  48. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  49. 2026-10-12 15:39 UTCEG score recompute
  50. 2026-10-12 05:35 UTCVendor advisory
  51. 2026-10-11 19:24 UTCEG score recompute
  52. 2026-10-11 16:40 UTCEG score recompute
  53. 2026-10-11 13:59 UTCEG score recompute
  54. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  55. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  56. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  57. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  58. 2026-10-08 09:49 UTCVendor advisory
  59. 2026-10-08 06:10 UTCEG score recompute
  60. 2026-10-08 06:10 UTCVendor advisory
  61. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  62. 2026-10-07 08:58 UTCVendor advisory
  63. 2026-10-07 05:19 UTCVendor advisory
  64. 2026-10-07 01:16 UTCVendor advisory
  65. 2026-10-06 21:20 UTCVendor advisory
  66. 2026-10-06 16:57 UTCEG score recompute
  67. 2026-10-06 16:57 UTCVendor advisory
  68. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  69. 2026-10-06 12:24 UTCVendor advisory
  70. 2026-10-06 07:54 UTCVendor advisory
  71. 2026-10-06 03:43 UTCEG score recompute
  72. 2026-10-06 03:43 UTCVendor advisory
  73. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  74. 2026-10-05 17:33 UTCVendor advisory
  75. 2026-10-05 13:52 UTCVendor advisory

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Frequently asked(5)

What is CVE-2026-75595?
CVE-2026-75595 is a critical-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.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause…
When was the CVE record for CVE-2026-75595 published?
The CVE record for CVE-2026-75595 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-2026-75595 actively exploited?
CVE-2026-75595 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-2026-75595?
CVE-2026-75595 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-75595?
A fix for CVE-2026-75595 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-75595 are linked in the Vendor Advisories panel on this page.

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