Webpack is a module bundler. From version 5.49.0 to before 5.104.0, when experiments.buildHttp is enabled, webpack’s HTTP(S) resolver (HttpUriPlugin) enforces allowedUris only for the initial URL, but does not re-validate allowedUris after following HTTP 30x redirects. As a result, an import that appears restricted to a trusted allow-list can be redirected to HTTP(S) URLs outside the allow-list. This is a policy/allow-list bypass that enables build-time SSRF behavior (requests from the build machine to internal-only endpoints, depending on network access) and untrusted content inclusion in build outputs (redirected content is treated as module source and bundled). This issue has been patched in version 5.104.0.

Webpack is a module bundler. From version 5.49.0 to before 5.104.1, when experiments.buildHttp is enabled, webpack’s HTTP(S) resolver (HttpUriPlugin) can be bypassed to fetch resources from hosts outside allowedUris by using crafted URLs that include userinfo (username:password@host). If allowedUris enforcement relies on a raw string prefix check (e.g., uri.startsWith(allowed)), a URL that looks allow-listed can pass validation while the actual network request is sent to a different authority/host after URL parsing. This is a policy/allow-list bypass that enables build-time SSRF behavior (outbound requests from the build machine to internal-only endpoints, depending on network access) and untrusted content inclusion (the fetched response is treated as module source and bundled). This issue has been patched in version 5.104.1.