# CVE-2026-59903

## Summary

- **CVE ID:** CVE-2026-59903
- **Severity:** MEDIUM
- **CVSS Score:** 6.5 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N)
- **CWE:** CWE-524
- **Published:** Aug 17, 2026
- **Last Modified:** Aug 17, 2026

## Description

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.

## Affected Products

- netty — netty (< 4.1.137.Final)
- netty — netty (>= 4.2.0.Final, < 4.2.17.Final)

## References

- [CNA](https://github.com/netty/netty/security/advisories/GHSA-8c42-7qj2-3j46)
- [CNA](https://github.com/netty/netty/pull/17213)
- [CNA](https://github.com/netty/netty/pull/17217)
- [CNA](https://github.com/netty/netty/releases/tag/netty-4.1.137.Final)
- [CNA](https://github.com/netty/netty/releases/tag/netty-4.2.17.Final)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.24%
- **EPSS Percentile:** 15.7

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._