{"id":"CVE-2026-104871","revision":null,"records":[{"revision":"532d06a2eb794211a3d2d13b07e6dfaa","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-104871","aliases":[],"title":"Angular SSR: Path Traversal to Sibling Directories in CommonEngine on Windows","description":"The Angular SSR is a server-rise rendering tool for Angular applications. Prior to versions 20.3.36, 21.2.23, and 22.1.7, the CommonEngine retrieveSSGPage prerendered-page retrieval logic in @angular/ssr/node, and in @angular/ssr for versions 17 through 18, accepts a relative request URL containing a backslash parent-traversal segment on Windows. The non-special resolve:// URL base preserves the backslash, path.join interprets it as a Windows separator, and the pagePath.startsWith(normalize(publicPath)) check incorrectly accepts a sibling output directory whose name shares the configured public-directory prefix. An unauthenticated requester can therefore retrieve a sibling prerendered HTML page when that page contains the Angular SSG marker. The issue is limited to Windows deployments that pass relative request URLs to CommonEngine.render, have a prefix-sharing sibling output directory, and contain qualifying prerendered Angular HTML; it does not provide arbitrary file read. 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The issue is limited to Windows deployments that pass relative request URLs to CommonEngine.render, have a prefix-sharing sibling output directory, and contain qualifying prerendered Angular HTML; it does not provide arbitrary file read. This issue is fixed in versions 20.3.36, 21.2.23, and 22.1.7.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","score":6.3,"severity":null}],"references":["https://github.com/angular/angular-cli/security/advisories/GHSA-7g7c-h8rr-7p6q","https://github.com/angular/angular-cli/commit/645e41a47d21b7651837a4250de99af0509626e2","https://github.com/angular/angular-cli/commit/70748ca8e76fe4b42798719410336119d943e755","https://github.com/angular/angular-cli/commit/bb72145f9ab45aee29f523236b3a25cd0813a841","https://github.com/angular/angular-cli/commit/c3e5982e49705f0f6a913cb94622b4c555d2d914","https://github.com/angular/angular-cli/releases/tag/v20.3.36","https://github.com/angular/angular-cli/releases/tag/v21.2.23","https://github.com/angular/angular-cli/releases/tag/v22.1.7"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-91778","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Oct 2, 2026, 7:43:50 PM","dateUpdated":"Oct 2, 2026, 8:12:49 PM"},"relatedAdvisories":[{"id":"WID-SEC-W-2026-3745","title":"Angular: Schwachstelle ermöglicht Offenlegung von Informationen","vulnerabilityIds":["CVE-2026-104871"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-91778","identifiers":["EUVD-2026-91778","CVE-2026-104871","GHSA-7g7c-h8rr-7p6q"]},"retained":false,"historicalAffected":[]},{"revision":"769b6fd1292f4c9eaf28ae066576e10c","observedAt":"2026-10-25T04:17:29.458+00:00","statement":{"source":"nvd","id":"CVE-2026-104871","aliases":[],"title":"The Angular SSR is a server-rise rendering tool for Angular applications. Prior to versions 20.3.36, 21.2.23, and 22.1.7, the CommonEngine retrieveSSGPage prerendered-page retrieval logic in @angular/ssr/node, and in @angular/ssr for versio…","description":"The Angular SSR is a server-rise rendering tool for Angular applications. Prior to versions 20.3.36, 21.2.23, and 22.1.7, the CommonEngine retrieveSSGPage prerendered-page retrieval logic in @angular/ssr/node, and in @angular/ssr for versions 17 through 18, accepts a relative request URL containing a backslash parent-traversal segment on Windows. The non-special resolve:// URL base preserves the backslash, path.join interprets it as a Windows separator, and the pagePath.startsWith(normalize(publicPath)) check incorrectly accepts a sibling output directory whose name shares the configured public-directory prefix. An unauthenticated requester can therefore retrieve a sibling prerendered HTML page when that page contains the Angular SSG marker. The issue is limited to Windows deployments that pass relative request URLs to CommonEngine.render, have a prefix-sharing sibling output directory, and contain qualifying prerendered Angular HTML; it does not provide arbitrary file read. This issue is fixed in versions 20.3.36, 21.2.23, and 22.1.7.","state":0,"publishedAt":"2026-10-02T20:17:00.91+00:00","modifiedAt":"2026-10-06T16:00:36.547+00:00","affected":[],"metrics":[{"system":"CVSS 4.0 · security-advisories@github.com · Secondary","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","score":6.3,"severity":"MEDIUM"}],"references":["https://github.com/angular/angular-cli/commit/645e41a47d21b7651837a4250de99af0509626e2","https://github.com/angular/angular-cli/commit/70748ca8e76fe4b42798719410336119d943e755","https://github.com/angular/angular-cli/commit/bb72145f9ab45aee29f523236b3a25cd0813a841","https://github.com/angular/angular-cli/commit/c3e5982e49705f0f6a913cb94622b4c555d2d914","https://github.com/angular/angular-cli/releases/tag/v20.3.36","https://github.com/angular/angular-cli/releases/tag/v21.2.23","https://github.com/angular/angular-cli/releases/tag/v22.1.7","https://github.com/angular/angular-cli/security/advisories/GHSA-7g7c-h8rr-7p6q"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-104871","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Awaiting Analysis","weaknesses":["CWE-22"],"productCriteria":[],"sourceDates":{"published":"2026-10-02T20:17:00.910","lastModified":"2026-10-06T16:00:36.547"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-104871","identifiers":["CVE-2026-104871"]},"retained":false,"historicalAffected":[]},{"revision":"a12484276e414ebe9800ddac42c83af1","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-7g7c-h8rr-7p6q","aliases":["CVE-2026-104871"],"title":"Angular SSR: Path Traversal to Sibling Directories in CommonEngine on Windows","description":"A Path Traversal vulnerability exists in the prerendered (SSG) page retrieval logic of `CommonEngine` in `@angular/ssr/node` (and `@angular/ssr` in earlier versions). When deployed on Windows, an attacker can craft a request path with backslash directory traversal sequences that causes `CommonEngine` to serve prerendered pages from sibling output directories.\n\nThe vulnerability occurs due to how relative URLs and Windows file paths are resolved and validated:\n\n1. A request URL containing a backslash parent traversal segment (e.g., `/..\\app-admin`) is passed to `CommonEngine.render({ url })`.\n2. The engine parses the URL using `new URL(url, 'resolve://')`. Because `resolve://` is a non-special scheme under the WHATWG URL standard, backslashes are not normalized to forward slashes, leaving the `pathname` unnormalized as `/..\\app-admin`.\n3. The engine constructs the candidate file path using `join(publicPath, pathname, 'index.html')`. On Windows, `path.join` treats `\\` as a path delimiter, resolving the parent segment (`..\\`) out of `publicPath` (e.g., `dist\\app`) into a sibling directory (e.g., `dist\\app-admin\\index.html`).\n4. The containment check (`pagePath.startsWith(normalize(publicPath))`) performs a prefix match without a trailing path delimiter. Because the sibling folder name starts with the configured public folder name (e.g., `dist\\app-admin` starts with `dist\\app`), the check erroneously succeeds.\n5. If the target file exists and contains the Angular SSG marker (`ng-server-context=\"...ssg...\"`), `CommonEngine` reads and serves the sibling page instead of rendering the requested route.\n\n### Impact\n\nThis vulnerability allows unauthorized access to prerendered static pages from adjacent applications or build outputs:\n\n- **Information Disclosure:** Prerendered HTML pages located in sibling directories sharing the same name prefix as the public directory (e.g., an internal administration app `app-admin` adjacent to `app`) can be accessed by unauthorized users.\n- **Limited Scope:** Only HTML files matching the Angular SSG marker regex are served. Arbitrary non-Angular files, secrets, or configuration files without the SSG context attribute cannot be read through this mechanism.\n\n### Attack Preconditions\n\n- The application must use `CommonEngine` from `@angular/ssr/node` (or `@angular/ssr` in v17–v18).\n- The application must be hosted on Windows (where Node's `path.join` resolves `\\` as a path separator).\n- The application passes a relative request URL (such as `req.url` or `req.originalUrl` without origin) into `CommonEngine.render({ url })`.\n- A sibling directory exists whose name starts with the same prefix as the configured `publicPath` directory (e.g., `dist\\app-admin` alongside `dist\\app`).\n- The targeted sibling directory contains prerendered HTML output containing the Angular SSG marker.\n\n### Affected Versions\n\n- `>= 22.0.0, < 22.1.7`\n- `>= 21.0.0, < 21.2.23`\n- `>= 20.0.0, < 20.3.36`\n- `<= 19.2.27`\n\n### Patches\n\n- `22.1.7`\n- `21.2.23`\n- `20.3.36`\n\n> Versions `<= 19.2.27` have reached End of Support / LTS expiration and will not be patched.\n\n### Workarounds\n\nUntil a patch is applied, developers using `CommonEngine` on Windows can sanitize request URLs in `server.ts` before passing them to `CommonEngine.render`, ensuring backslashes are replaced or that an absolute HTTP URL is constructed:\n\n```ts\nserver.use((req, res, next) => {\n  const { protocol, originalUrl, headers } = req;\n\n  // Normalize backslashes or construct a full HTTP URL (which forces WHATWG URL normalization)\n  const sanitizedUrl = `${protocol}://${headers.host}${originalUrl.replace(/\\\\/g, '/')}`;\n\n  commonEngine\n    .render({\n      bootstrap,\n      documentFilePath: indexHtml,\n      url: sanitizedUrl,\n      publicPath: distFolder,\n    })\n    .then((html) => res.send(html))\n    .catch((err) => next(err));\n});\n```\n\nAlternatively, migrate from the deprecated `CommonEngine` to `AngularNodeAppEngine`, which relies on manifest-based route matching rather than direct filesystem path resolution.","state":0,"publishedAt":"2026-10-05T22:53:45+00:00","modifiedAt":"2026-10-05T23:00:04.2452309+00:00","affected":[{"ecosystem":"npm","name":"@angular/ssr","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"22.0.0"},{"kind":"fixed","version":"22.1.7"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"npm","name":"@angular/ssr","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"21.0.0"},{"kind":"fixed","version":"21.2.23"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"npm","name":"@angular/ssr","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"20.0.0"},{"kind":"fixed","version":"20.3.36"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"npm","name":"@angular/ssr","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"last_affected","version":"19.2.27"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V4","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/angular/angular-cli/security/advisories/GHSA-7g7c-h8rr-7p6q","https://nvd.nist.gov/vuln/detail/CVE-2026-104871","https://github.com/angular/angular-cli/commit/645e41a47d21b7651837a4250de99af0509626e2","https://github.com/angular/angular-cli/commit/70748ca8e76fe4b42798719410336119d943e755","https://github.com/angular/angular-cli/commit/bb72145f9ab45aee29f523236b3a25cd0813a841","https://github.com/angular/angular-cli/commit/c3e5982e49705f0f6a913cb94622b4c555d2d914","https://github.com/angular/angular-cli","https://github.com/angular/angular-cli/releases/tag/v20.3.36","https://github.com/angular/angular-cli/releases/tag/v21.2.23","https://github.com/angular/angular-cli/releases/tag/v22.1.7"],"sourceUrl":"https://github.com/advisories/GHSA-7g7c-h8rr-7p6q","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-7g7c-h8rr-7p6q","identifiers":["GHSA-7g7c-h8rr-7p6q","CVE-2026-104871"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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