CVE-2026-75596

HIGHPre-NVD 8.78.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 72% 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
Trending — 3 sources updated this week
8.7EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.7Exploit: 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.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
8.7
EG Score
8.7(medium)
EG Risk
54(Track)
EG Risk 54/100SSVC: 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
Severity87% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
28%
KEV
Not listed

Published

August 19, 2026

Last Modified

August 20, 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_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 Patch Available

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 15× in last 7d / 15× 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. 2026-08-25 16:31 UTCEG score recompute
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-24 17:18 UTCEG score recompute
  4. 2026-08-24 14:18 UTCEPSS rescore
  5. 2026-08-23 06:25 UTCEG score recompute
  6. 2026-08-23 00:19 UTCEPSS rescore
  7. 2026-08-22 07:12 UTCEG score recompute
  8. 2026-08-21 23:49 UTCEPSS rescore
  9. 2026-08-21 07:58 UTCEG score recompute
  10. 2026-08-20 22:56 UTCEPSS rescore
  11. 2026-08-20 20:20 UTCEG score recompute
  12. 2026-08-20 20:02 UTCEG score recompute
  13. 2026-08-19 21:19 UTCEG score recompute
  14. 2026-08-19 21:04 UTCEG score recompute
  15. 2026-08-19 21:03 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-75596?
CVE-2026-75596 is a high vulnerability 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 CVE-2026-75596 disclosed?
CVE-2026-75596 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-2026-75596 actively exploited?
CVE-2026-75596 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 72.3% of all scored CVEs.
What is the CVSS score of CVE-2026-75596?
CVE-2026-75596 has a CVSS v3 base score of 8.7 (NVD).
How do I remediate CVE-2026-75596?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-75596, 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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