CVE-2026-75595

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 76% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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
9.1(medium)
EG Risk
41(Track)
EG Risk 41/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
24%
KEV
Not listed

Published

August 19, 2026

Last Modified

August 20, 2026

Advisory Details (7)

Auto-updated Aug 29, 2026
Patch available. Sources: github_release, github, github_commit, github_pr.
github Patch Available

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_pr 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_pr 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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 24× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

  1. 2026-08-30 04:55 UTCEG score recompute
  2. 2026-08-30 01:22 UTCEPSS rescore
  3. 2026-08-29 01:45 UTCEG score recompute
  4. 2026-08-28 21:42 UTCEPSS rescore
  5. 2026-08-27 15:52 UTCEG score recompute
  6. 2026-08-27 14:25 UTCEPSS rescore
  7. 2026-08-26 17:54 UTCEG score recompute
  8. 2026-08-26 14:47 UTCEPSS rescore
  9. 2026-08-25 16:06 UTCEG score recompute
  10. 2026-08-25 13:49 UTCEPSS rescore
  11. 2026-08-24 14:32 UTCEG score recompute
  12. 2026-08-24 14:18 UTCEPSS rescore
  13. 2026-08-24 10:53 UTCEG score recompute
  14. 2026-08-23 01:58 UTCEG score recompute
  15. 2026-08-23 00:19 UTCEPSS rescore
  16. 2026-08-22 00:25 UTCEG score recompute
  17. 2026-08-21 23:49 UTCEPSS rescore
  18. 2026-08-21 02:25 UTCEG score recompute
  19. 2026-08-20 22:56 UTCEPSS rescore
  20. 2026-08-20 15:28 UTCEG score recompute
  21. 2026-08-20 14:27 UTCEG score recompute
  22. 2026-08-20 00:57 UTCEG score recompute
  23. 2026-08-19 21:18 UTCEG score recompute
  24. 2026-08-19 21:17 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-75595?
CVE-2026-75595 is a critical vulnerability 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 CVE-2026-75595 disclosed?
CVE-2026-75595 was first published in the National Vulnerability Database on August 19, 2026, with the most recent update on August 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-75595 actively exploited?
CVE-2026-75595 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 75.9% of all 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?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-75595, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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