CVE-2026-75596

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.4% (29th percentile of EPSS-scored CVEs). 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, nvd
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • 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 49/100CISA SSVC

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
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
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
29th
KEV
Not listed

CISA SSVCTrack 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). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 19, 2026

Last Modified

September 22, 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
githubMentions 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.

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 11× in last 7d / 51× 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. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:13 UTCEPSS rescore
  3. 2026-10-08 06:16 UTCEG score recompute
  4. 2026-10-07 23:48 UTCEPSS rescore
  5. 2026-10-06 19:31 UTCEG score recompute
  6. 2026-10-06 15:18 UTCEPSS rescore
  7. 2026-10-06 07:54 UTCEG score recompute
  8. 2026-10-05 17:43 UTCEPSS rescore
  9. 2026-10-05 05:07 UTCEG score recompute
  10. 2026-10-04 23:22 UTCEPSS rescore
  11. 2026-10-03 16:53 UTCEG score recompute
  12. 2026-10-03 14:26 UTCEPSS rescore
  13. 2026-10-02 22:00 UTCEG score recompute
  14. 2026-10-01 22:45 UTCEG score recompute
  15. 2026-10-01 19:50 UTCEPSS rescore
  16. 2026-09-30 20:33 UTCEG score recompute
  17. 2026-09-30 08:35 UTCEG score recompute
  18. 2026-09-29 15:24 UTCEPSS rescore
  19. 2026-09-28 21:41 UTCEG score recompute
  20. 2026-09-28 13:52 UTCEPSS rescore
  21. 2026-09-27 16:08 UTCEG score recompute
  22. 2026-09-27 13:48 UTCEPSS rescore
  23. 2026-09-27 04:22 UTCEG score recompute
  24. 2026-09-26 15:59 UTCEPSS rescore
  25. 2026-09-26 00:28 UTCEPSS rescore
Show 70 more
  1. 2026-09-24 19:31 UTCEG score recompute
  2. 2026-09-24 14:04 UTCEPSS rescore
  3. 2026-09-23 20:07 UTCEG score recompute
  4. 2026-09-23 17:54 UTCEPSS rescore
  5. 2026-09-22 19:33 UTCEG score recompute▼ 1.20
  6. 2026-09-22 19:32 UTCNVD updateCVSS v3 → 7.5
  7. 2026-09-22 16:01 UTCEPSS rescore
  8. 2026-09-22 08:13 UTCEG score recompute
  9. 2026-09-21 21:09 UTCEPSS rescore
  10. 2026-09-20 21:10 UTCEG score recompute
  11. 2026-09-20 20:16 UTCEPSS rescore
  12. 2026-09-19 21:52 UTCEG score recompute
  13. 2026-09-18 21:41 UTCEG score recompute
  14. 2026-09-18 19:28 UTCEPSS rescore
  15. 2026-09-17 21:28 UTCEG score recompute
  16. 2026-09-16 20:05 UTCEG score recompute
  17. 2026-09-16 14:08 UTCEPSS rescore
  18. 2026-09-16 06:28 UTCEG score recompute
  19. 2026-09-16 05:15 UTCEPSS rescore
  20. 2026-09-15 06:50 UTCEG score recompute
  21. 2026-09-15 03:12 UTCEPSS rescore
  22. 2026-09-13 19:31 UTCEG score recompute
  23. 2026-09-12 20:17 UTCEG score recompute
  24. 2026-09-12 15:02 UTCEPSS rescore
  25. 2026-09-11 21:03 UTCEG score recompute
  26. 2026-09-11 14:53 UTCEPSS rescore
  27. 2026-09-10 10:11 UTCEG score recompute
  28. 2026-09-10 09:35 UTCEPSS rescore
  29. 2026-09-09 02:14 UTCEG score recompute
  30. 2026-09-08 22:01 UTCEPSS rescore
  31. 2026-09-07 21:44 UTCEG score recompute
  32. 2026-09-06 22:24 UTCEG score recompute
  33. 2026-09-06 13:48 UTCEPSS rescore
  34. 2026-09-05 23:09 UTCEG score recompute
  35. 2026-09-04 23:54 UTCEG score recompute
  36. 2026-09-04 11:44 UTCEG score recompute
  37. 2026-09-04 05:07 UTCEPSS rescore
  38. 2026-09-03 00:29 UTCEG score recompute
  39. 2026-09-02 14:12 UTCEPSS rescore
  40. 2026-09-02 01:06 UTCEG score recompute
  41. 2026-09-01 13:54 UTCEPSS rescore
  42. 2026-09-01 13:27 UTCEG score recompute
  43. 2026-09-01 04:40 UTCEPSS rescore
  44. 2026-09-01 04:40 UTCEPSS rescore
  45. 2026-08-31 01:09 UTCEG score recompute
  46. 2026-08-30 19:18 UTCEPSS rescore
  47. 2026-08-30 19:17 UTCEPSS rescore
  48. 2026-08-30 01:55 UTCEG score recompute
  49. 2026-08-30 01:22 UTCEPSS rescore
  50. 2026-08-29 02:38 UTCEG score recompute
  51. 2026-08-28 21:42 UTCEPSS rescore
  52. 2026-08-27 15:37 UTCEG score recompute
  53. 2026-08-27 14:25 UTCEPSS rescore
  54. 2026-08-26 16:14 UTCEG score recompute
  55. 2026-08-26 14:47 UTCEPSS rescore
  56. 2026-08-25 16:31 UTCEG score recompute
  57. 2026-08-25 13:49 UTCEPSS rescore
  58. 2026-08-24 17:18 UTCEG score recompute
  59. 2026-08-24 14:18 UTCEPSS rescore
  60. 2026-08-23 06:25 UTCEG score recompute
  61. 2026-08-23 00:19 UTCEPSS rescore
  62. 2026-08-22 07:12 UTCEG score recompute
  63. 2026-08-21 23:49 UTCEPSS rescore
  64. 2026-08-21 07:58 UTCEG score recompute
  65. 2026-08-20 22:56 UTCEPSS rescore
  66. 2026-08-20 20:20 UTCEG score recompute
  67. 2026-08-20 20:02 UTCEG score recompute
  68. 2026-08-19 21:19 UTCEG score recompute
  69. 2026-08-19 21:04 UTCEG score recompute
  70. 2026-08-19 21:03 UTCMITRE cvelistV5first tracked

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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 on August 19, 2026, with the most recent update on September 22, 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 0.4% probability of exploitation in the next 30 days (29th 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.

Dependency Blast Radius

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