Reference page — cumulative record through Saturday, October 3, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-59903

CVE-2026-59903HIGH

Netty: Cache Poisoning and Information Disclosure via CORS Vary Header Overwrite

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  H  N  N    7.5   .0025   14.4     —

AFFECTED
  Product  Versions           Fixed
  netty    < 4.1.137.Final –  —

TIMELINE
  Jul 7   Reserved by GitHub_M
  Aug 17  Published (CNA: GitHub_M)
  Sep 23  RESCORED — CVE-2026-59903 (netty). CVSS 6.5 → 7.5 (NVD).

CWE-524 · CNA: GitHub_M · CVSS v3.1 · 5 references · NVD status: Analyzed

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
July 7, 2026	Reserved	Reserved by GitHub_M
August 17, 2026	Published	Published (CNA: GitHub_M)
September 23, 2026	RESCORED	RESCORED — CVE-2026-59903 (netty). CVSS 6.5 → 7.5 (NVD).

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
netty	netty	—	< 4.1.137.Final	—

Weaknesses

CWE-524

References (5)

https://github.com/netty/netty/pull/17213 [Issue Tracking, Patch]
https://github.com/netty/netty/pull/17217 [Issue Tracking, Patch]
https://github.com/netty/netty/releases/tag/netty-4.1.137.Final [Release Notes]
https://github.com/netty/netty/releases/tag/netty-4.2.17.Final [Release Notes]
https://github.com/netty/netty/security/advisories/GHSA-8c42-7qj2-3j46 [Vendor Advisory]

Authoritative record: CVE-2026-59903 at cve.org

Vendors: netty

Weaknesses: CWE-524

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-59903 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Saturday, October 3, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.