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. 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
Sources: EPSS, NVD CVSS

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
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
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-11). 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

Patch Availability(5)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatnetty-handler2026-11-06redhat
redhatrhbk/keycloak-rhel9-operator:26.4-302026-11-06redhat
redhatrhbk/keycloak-rhel9-operator:26.6-242026-11-06redhat
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 22× in last 7d / 73× 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 → 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 265 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 165 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 0.3% · 24th percentile
  2. 2026-11-12 15:59 UTCEchelonGraph re-scored
  3. 2026-11-12 15:59 UTCVendor advisory
  4. 2026-11-12 15:59 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  5. 2026-11-11 16:40 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  6. 2026-11-11 15:47 UTCEchelonGraph re-scored
  7. 2026-11-11 15:47 UTCVendor advisory
  8. 2026-11-11 15:47 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  9. 2026-11-10 16:45 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  10. 2026-11-10 15:39 UTCEchelonGraph re-scored
  11. 2026-11-10 15:39 UTCVendor advisory
  12. 2026-11-10 15:39 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  13. 2026-11-09 16:36 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  14. 2026-11-09 15:31 UTCEchelonGraph re-scored
  15. 2026-11-09 15:31 UTCVendor advisory
  16. 2026-11-09 15:31 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  17. 2026-11-08 16:40 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  18. 2026-11-08 15:23 UTCEchelonGraph re-scored
  19. 2026-11-08 15:23 UTCVendor advisory
  20. 2026-11-08 15:23 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  21. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  22. 2026-11-07 15:15 UTCEchelonGraph re-scored
  23. 2026-11-07 15:15 UTCVendor advisory
  24. 2026-11-07 15:15 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  25. 2026-11-06 17:55 UTCOSV refresh
Show 75 more
  1. 2026-11-06 16:39 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  2. 2026-11-06 15:07 UTCEchelonGraph re-scored
  3. 2026-11-06 15:07 UTCVendor advisory
  4. 2026-11-06 15:07 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  5. 2026-11-05 14:59 UTCEchelonGraph re-scored
  6. 2026-11-05 14:59 UTCVendor advisory
  7. 2026-11-05 14:59 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  8. 2026-11-04 16:36 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  9. 2026-11-04 14:51 UTCEchelonGraph re-scored
  10. 2026-11-04 14:51 UTCVendor advisory
  11. 2026-11-04 14:51 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  12. 2026-11-03 16:49 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  13. 2026-11-03 14:43 UTCEchelonGraph re-scored
  14. 2026-11-03 14:43 UTCVendor advisory
  15. 2026-11-03 14:43 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  16. 2026-11-02 16:46 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  17. 2026-11-02 14:14 UTCEchelonGraph re-scored
  18. 2026-11-02 14:14 UTCVendor advisory
  19. 2026-11-02 14:14 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  20. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  21. 2026-11-01 14:07 UTCVendor advisory
  22. 2026-11-01 14:07 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  23. 2026-11-01 07:39 UTCGHSA enrichmentGHSA-c4c3-7fpv-j4q5 · GitHub severity CRITICAL
  24. 2026-11-01 07:39 UTCEchelonGraph re-scored
  25. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  26. 2026-10-31 13:57 UTCEchelonGraph re-scored
  27. 2026-10-31 13:57 UTCVendor advisory
  28. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  29. 2026-10-30 13:50 UTCEchelonGraph re-scored
  30. 2026-10-30 13:50 UTCVendor advisory
  31. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  32. 2026-10-29 13:39 UTCEchelonGraph re-scored
  33. 2026-10-29 13:39 UTCVendor advisory
  34. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  35. 2026-10-28 13:29 UTCEchelonGraph re-scored
  36. 2026-10-28 13:29 UTCVendor advisory
  37. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  38. 2026-10-27 13:12 UTCVendor advisory
  39. 2026-10-27 10:35 UTCEchelonGraph re-scored
  40. 2026-10-27 10:35 UTCVendor advisory
  41. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  42. 2026-10-26 10:26 UTCVendor advisory
  43. 2026-10-26 09:42 UTCEchelonGraph re-scored
  44. 2026-10-26 09:42 UTCVendor advisory
  45. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  46. 2026-10-25 14:02 UTCEchelonGraph re-scored
  47. 2026-10-25 09:34 UTCEchelonGraph re-scored
  48. 2026-10-25 09:34 UTCVendor advisory
  49. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  50. 2026-10-24 09:26 UTCEchelonGraph re-scored
  51. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  52. 2026-10-23 09:18 UTCEchelonGraph re-scored
  53. 2026-10-23 09:18 UTCVendor advisory
  54. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  55. 2026-10-22 09:10 UTCEchelonGraph re-scored
  56. 2026-10-22 09:10 UTCVendor advisory
  57. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  58. 2026-10-21 09:02 UTCEchelonGraph re-scored
  59. 2026-10-21 09:02 UTCVendor advisory
  60. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  61. 2026-10-20 08:53 UTCEchelonGraph re-scored
  62. 2026-10-20 08:53 UTCVendor advisory
  63. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  64. 2026-10-19 08:44 UTCEchelonGraph re-scored
  65. 2026-10-19 08:44 UTCVendor advisory
  66. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  67. 2026-10-18 08:36 UTCVendor advisory
  68. 2026-10-18 03:13 UTCEchelonGraph re-scored
  69. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  70. 2026-10-17 07:23 UTCEchelonGraph re-scored
  71. 2026-10-17 07:23 UTCVendor advisory
  72. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  73. 2026-10-16 07:14 UTCEchelonGraph re-scored
  74. 2026-10-16 07:14 UTCVendor advisory
  75. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 18th percentile

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 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.

Dependency Blast Radius

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