Use of cache containing sensitive information in Netty - CVE-2026-59903
Published: August 8, 2026
Vulnerability identifier: #VU141321
CSH Severity: Medium
CVSS v4: 8.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-59903
CWE-ID: CWE-524
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to use of cache containing sensitive information in io.netty.handler.codec.http.cors.CorsHandler#setVaryHeader when handling responses behind a caching proxy or CDN. A remote attacker can trigger caching of user-specific responses with an overwritten Vary header to disclose sensitive information.
This affects Netty-based web applications that use CorsHandler, set their own Vary headers for authenticated or user-specific responses, and are deployed behind an intermediate cache.
Affected software
Netty
How to mitigate CVE-2026-59903
Install security update from vendor's website.
Netty - addressed in versions 4.1.137, 4.2.17