{"id":"CVE-2026-56746","aliases":["GHSA-6cqp-g7gg-8hr5"],"url":"https://o3.security/vulnerability/CVE-2026-56746","summary":"Netty has a Security Control Bypass via CORS Short-Circuit Failure","details":"### Summary\nNetty'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.\n\n### Details\nIn `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.\n\nThe vulnerability is located in the `getForOrigin` method:\n\n```java\n            if (corsConfig.isNullOriginAllowed() || NULL_ORIGIN.equals(requestOrigin)) {\n                return corsConfig;\n            }\n```\n\nIf 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.\n\n### Impact\nApplications 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.","published":"2026-07-21T21:36:18.627Z","modified":"2026-10-21T02:31:07.680587593Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N"},"epss":{"score":0.00379,"percentile":0.31431,"asOf":"2026-09-15"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Maven","name":"io.netty:netty-codec-http","fixedVersion":"4.2.16.Final"},{"ecosystem":"Maven","name":"io.netty:netty-codec-http","fixedVersion":"4.1.136.Final"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/netty/netty/releases/tag/netty-4.1.136.Final"},{"type":"WEB","url":"https://github.com/netty/netty/releases/tag/netty-4.2.16.Final"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56746.json"},{"type":"ADVISORY","url":"https://github.com/netty/netty/security/advisories/GHSA-6cqp-g7gg-8hr5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56746"},{"type":"PACKAGE","url":"https://github.com/netty/netty"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:31:07.680587593Z"}}