Netty: Security Control Bypass via CORS Short-Circuit Failure

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS

• CVE-2026-56746: 0.41% estimated exploitation activity in the next 30 days; percentile 35.14 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 an attacker sends Origin: null,…

Published by the source

22 Jul 2026, 21:42 UTC

Last modified by the source

22 Jul 2026, 21:42 UTC

Source last checked

26 Oct 2026, 16:54 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6cqp-g7gg-8hr5

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# Patch Next advisory brief: CVE-2026-56746

Advisory: Netty: Security Control Bypass via CORS Short-Circuit Failure
IDs: CVE-2026-56746, GHSA-6cqp-g7gg-8hr5
Record: https://patchnext.com/advisories/cve-2026-56746 (revision 1, source checked 26 Oct 2026, 16:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: io.netty:netty-codec-http 4.2.16.Final, 4.1.136.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.netty:netty-codec-http: affected >= 4.2.0.Final, < 4.2.16.Final; < 4.1.136.Final; fixed in 4.2.16.Final, 4.1.136.Final

## Suggested inspection (read-only)
- Maven io.netty:netty-codec-http: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on io.netty:netty-codec-http.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6cqp-g7gg-8hr5 (GitHub-reviewed advisory GHSA-6cqp-g7gg-8hr5 lists affected ranges: Maven io.netty:netty-codec-http >=4.2.0.Final =0 <4.1.136.Final)

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