Medium 6.5Published Aug 17, 2026

CVE-2026-59903Netty: Cache Poisoning and Information Disclosure via CORS Vary Header Overwrite

Updated under an hour ago (2026-10-19 05:50 UTC)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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: 6.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
Weakness (CWE): CWE-524
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Aug 17, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

netty netty netty:netty (from the name)	before 4.1.137.Final; from 4.2.0.Final, < 4.2.17.Final	CNA record
netty netty netty:netty	before 4.1.137; from 4.2.0 before 4.2.17	NVD

References

https://github.com/netty/netty/security/advisories/GHSA-8c42-7qj2-3j46x-refsource-confirm, vendor-advisory
https://github.com/netty/netty/pull/17213x-refsource-misc, issue-tracking, patch
https://github.com/netty/netty/pull/17217x-refsource-misc, issue-tracking, patch
https://github.com/netty/netty/releases/tag/netty-4.1.137.Finalx-refsource-misc, release-notes
https://github.com/netty/netty/releases/tag/netty-4.2.17.Finalx-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.