Vulnerability · Published Aug 17, 2026 · Assigned by GitHub_M
CVE-2026-59903Netty: Cache Poisoning and Information Disclosure via CORS Vary Header Overwrite
Medium 6.5
In plain English
A medium-severity security flaw in netty from netty. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | netty | no fix listed | DEBIAN-CVE-2026-59903 |
| Debian:13 | netty | no fix listed | DEBIAN-CVE-2026-59903 |
| Debian:14 | netty | no fix listed | DEBIAN-CVE-2026-59903 |
| Maven | io.netty:netty-codec-http | 4.2.17.Final | GHSA-8c42-7qj2-3j46 |
| Maven | io.netty:netty-codec-http | 4.1.137.Final | GHSA-8c42-7qj2-3j46 |
| Ubuntu:26.10 | netty | no fix listed | UBUNTU-CVE-2026-59903 |
Affected products (as reported)
Weakness: CWE-524 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
References
- https://github.com/netty/netty/security/advisories/GHSA-8c42-7qj2-3j46 x_refsource_CONFIRM
- https://github.com/netty/netty/pull/17213 x_refsource_MISC
- https://github.com/netty/netty/pull/17217 x_refsource_MISC
- https://github.com/netty/netty/releases/tag/netty-4.1.137.Final x_refsource_MISC
- https://github.com/netty/netty/releases/tag/netty-4.2.17.Final x_refsource_MISC