CVE-2026-59903

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 84% 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
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: 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, io.netty.handler.codec.http.cors.CorsHandler setVaryHeader replaces application Vary headers such as Authorization or Cookie with Origin, allowing a caching proxy or CDN to reuse authenticated responses across users and disclose sensitive information. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
16%
KEV
Not listed

Published

August 17, 2026

Last Modified

September 10, 2026

Advisory Details (5)

Auto-updated Aug 17, 2026
Patch available. Sources: github, github_pr, 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_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

Cache Poisoning and Information Disclosure via CORS Vary Header Overwrite · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-8c42-7qj2-3j46

Vendor Advisories for CVE-2026-59903(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 rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-9 (12 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-16 (8 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
netty1:4.1.48-10 ... 1:4.1.48-16 (7 versions)——
Maven(1)
PackageVulnerable rangeFixed inDependents
io.netty:netty-codec-http4.0.0.Alpha1 ... 4.1.99.Final (230 versions)4.1.137.Final—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× 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. 2026-09-19 00:10 UTCEG score recompute
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-18 00:18 UTCEG score recompute
  4. 2026-09-17 19:31 UTCEPSS rescore
  5. 2026-09-16 23:07 UTCEG score recompute
  6. 2026-09-16 14:08 UTCEPSS rescore
  7. 2026-09-16 05:15 UTCEPSS rescore
  8. 2026-09-15 21:27 UTCEG score recompute
  9. 2026-09-15 03:11 UTCEPSS rescore
  10. 2026-09-13 20:32 UTCEG score recompute
  11. 2026-09-13 16:47 UTCEPSS rescore
  12. 2026-09-12 20:41 UTCEG score recompute
  13. 2026-09-11 20:51 UTCEG score recompute
  14. 2026-09-11 14:53 UTCEPSS rescore
  15. 2026-09-10 20:59 UTCEG score recompute
  16. 2026-09-10 09:35 UTCEPSS rescore
  17. 2026-09-09 05:35 UTCEG score recompute
  18. 2026-09-08 22:01 UTCEPSS rescore
  19. 2026-09-08 05:44 UTCEG score recompute
  20. 2026-09-07 16:01 UTCEPSS rescore
  21. 2026-09-07 05:32 UTCEG score recompute
  22. 2026-09-06 13:47 UTCEPSS rescore
  23. 2026-09-06 05:28 UTCEG score recompute
  24. 2026-09-05 05:38 UTCEG score recompute
  25. 2026-09-04 05:48 UTCEG score recompute
Show 34 more
  1. 2026-09-04 05:07 UTCEPSS rescore
  2. 2026-09-03 05:49 UTCEG score recompute
  3. 2026-09-02 14:12 UTCEPSS rescore
  4. 2026-09-02 05:00 UTCEG score recompute
  5. 2026-09-01 13:54 UTCEPSS rescore
  6. 2026-09-01 05:06 UTCEG score recompute
  7. 2026-09-01 04:40 UTCEPSS rescore
  8. 2026-08-31 05:13 UTCEG score recompute
  9. 2026-08-30 19:17 UTCEPSS rescore
  10. 2026-08-30 05:23 UTCEG score recompute
  11. 2026-08-30 01:22 UTCEPSS rescore
  12. 2026-08-29 05:29 UTCEG score recompute
  13. 2026-08-28 21:42 UTCEPSS rescore
  14. 2026-08-27 19:25 UTCEG score recompute
  15. 2026-08-27 14:25 UTCEPSS rescore
  16. 2026-08-26 18:18 UTCEG score recompute
  17. 2026-08-26 14:46 UTCEPSS rescore
  18. 2026-08-25 18:21 UTCEG score recompute
  19. 2026-08-25 13:49 UTCEPSS rescore
  20. 2026-08-24 18:30 UTCEG score recompute
  21. 2026-08-23 18:40 UTCEG score recompute
  22. 2026-08-23 00:19 UTCEPSS rescore
  23. 2026-08-22 18:50 UTCEG score recompute
  24. 2026-08-21 23:49 UTCEPSS rescore
  25. 2026-08-21 18:59 UTCEG score recompute
  26. 2026-08-20 22:55 UTCEPSS rescore
  27. 2026-08-19 19:16 UTCEG score recompute
  28. 2026-08-19 17:04 UTCEPSS rescore
  29. 2026-08-18 19:18 UTCEG score recompute
  30. 2026-08-18 13:48 UTCEPSS rescore
  31. 2026-08-17 19:27 UTCEG score recompute
  32. 2026-08-17 18:21 UTCEG score recompute
  33. 2026-08-17 18:10 UTCEG score recompute
  34. 2026-08-17 18:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-59903?
CVE-2026-59903 is a medium vulnerability published on August 17, 2026. Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Final and 4.2.17.Final, io.netty.handler.codec.http.cors.CorsHandler setVaryHeader replaces application Vary headers such as Authorization or Cookie with Origin, allowing a caching proxy or CDN to reuse…
When was CVE-2026-59903 disclosed?
CVE-2026-59903 was first published in the National Vulnerability Database on August 17, 2026, with the most recent update on September 10, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-59903 actively exploited?
CVE-2026-59903 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 83.9% of all scored CVEs.
What is the CVSS score of CVE-2026-59903?
CVE-2026-59903 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-59903?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-59903, 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.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-59903

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