Netty: Security Control Bypass via CORS Short-Circuit Failure
Summary
Netty's CorsHandler provides a shortCircuit() configuration designed to reject unauthorized cross-origin requests immediately, acting as a security control before requests reach the application. However, due to a logical operator error in the origin evaluation process, this protection can be entirely bypassed. An attacker can bypass the short-circuit mechanism by sending a request with an Origin: null header. This failure forwards unauthorized requests to the backend application, bypassing intended access controls.
Details
In io.netty.handler.codec.http.cors.CorsHandler#channelRead, the short-circuit logic relies on the configuration returned by getForOrigin(origin) to determine if an origin is authorized. If getForOrigin returns a configuration object, the short-circuit check (!(origin == null || config != null)) is bypassed, and the request proceeds to the backend.
The vulnerability is located in the getForOrigin method:
if (corsConfig.isNullOriginAllowed() || NULL_ORIGIN.equals(requestOrigin)) {
return corsConfig;
}If an attacker sends Origin: null, NULL_ORIGIN.equals(requestOrigin) evaluates to true. The method returns the configuration object regardless of whether isNullOriginAllowed() was configured by the developer. The short-circuit is bypassed.
Impact
Applications relying on CorsHandler's short-circuit feature to prevent unauthorized cross-origin requests from reaching their backend logic are completely exposed. The framework fails to enforce the developer's intended access controls, allowing unauthorized requests to be processed.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | io.netty:netty-codec-http | >= 4.2.0.Final, < 4.2.16.Final, < 4.1.136.Final | 4.2.16.Final, 4.1.136.Final |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N- Weakness (CWE)
CWE-284- Platform
- Java / Kotlin (Maven)
- Package
io.netty:netty-codec-http- Disclosed
- 22.07.2026
- Updated
- 11.10.2026 13:20
Sources and licenses
OSV / GitHub Advisory Database - GHSA-6cqp-g7gg-8hr5 - CC BY 4.0
Vulnerability history: io.netty:netty-codec-http
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 24
- First → latest
- 02.2020 08.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 6
- Medium 16
- Low 1
Disclosures per year
- 2020: 1
- 2021: 2
- 2022: 2
- 2023: 0
- 2024: 1
- 2025: 2
- 2026: 16
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