High severity · published Aug 17, 2026
CVE-2026-59903
Netty: Cache Poisoning and Information Disclosure via CORS Vary Header Overwrite
7.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 25% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NE
netty · netty
< 4.1.137.Final; >= 4.2.0.Final, < 4.2.17.Final · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-59903
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-59903
Issue Tracking
https://github.com/netty/netty/pull/17213
Issue Tracking
https://github.com/netty/netty/pull/17217
Release Notes
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
Vendor Advisory
https://github.com/netty/netty/security/advisories/GHSA-8c42-7qj2-3j46
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