CVE-2026-70606

Electron is a framework for writing cross-platform desktop applications using JavaScript, HTML and CSS. Prior to 40.10.6, 41.9.1, 42.5.1, and 43.0.0, when a custom protocol handler returned a ProtocolResponse with a url and no session, Electron made the upstream request through defaultSession instead of the session that handled the protocol. A cached response could then be reused across otherwise isolated session partitions. Apps that use ProtocolResponse.url, omit ProtocolResponse.session, and rely on separate sessions to isolate content are affected. This issue is fixed in versions 40.10.6, 41.9.1, 42.5.1, and 43.0.0.

Electron is a framework for writing cross-platform desktop applications using JavaScript, HTML and CSS. Prior to 40.10.6, 41.9.1, 42.5.1, and 43.0.0, when a custom protocol handler returned a ProtocolResponse with a url and no session, Electron made the upstream request through defaultSession instead of the session that handled the protocol. A cached response could then be reused across otherwise isolated session partitions. Apps that use ProtocolResponse.url, omit ProtocolResponse.session, and rely on separate sessions to isolate content are affected. This issue is fixed in versions 40.10.6, 41.9.1, 42.5.1, and 43.0.0.

### Impact When a custom protocol handler returned a `ProtocolResponse` with a `url` and no `session`, Electron made the upstream request through `defaultSession` instead of the session that handled the protocol. A cached response could then be reused across otherwise isolated session partitions. Apps that use `ProtocolResponse.url`, omit `ProtocolResponse.session`, and rely on separate sessions to isolate content are affected. Apps that set an explicit `session`, or that do not isolate content across sessions, are not affected. ### Workarounds Set `ProtocolResponse.session` explicitly so the request uses the intended session's cache. ### Fixed Versions * `43.0.0` * `42.5.1` * `41.9.1` * `40.10.6` ### For more information If you have any questions or comments about this advisory, email Electron at [[email protected]](mailto:[email protected])