Angular SSR: Path Traversal to Sibling Directories in CommonEngine on Windows

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

2 Oct 2026 19:43:50 UTC

Source modified

2 Oct 2026 20:12:49 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 4.0 · 6.3 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

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.

Source published

Oct 2, 2026, 7:43:50 PM (timezone not stated)

Source modified

Oct 2, 2026, 8:12:49 PM (timezone not stated)

Observed here

11 Nov 2026 05:30:37 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 6.3 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

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.

Source published

2 Oct 2026 20:17:00 UTC

Source modified

6 Oct 2026 16:00:36 UTC

Observed here

25 Oct 2026 04:17:29 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 6.3 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

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. The vulnerability occurs due to how relative URLs and Windows file paths are resolved and validated: 1. A request URL containing a backslash parent traversal segment (e.g., `/..\app-admin`) is passed to `CommonEngine.render({ url })`. 2. 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`. 3. 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`). 4. 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. 5. 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. ### Impact This vulnerability allows unauthorized access to prerendered static pages from adjacent applications or build outputs: - **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. - **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. ### Attack Preconditions - The application must use `CommonEngine` from `@angular/ssr/node` (or `@angular/ssr` in v17–v18). - The application must be hosted on Windows (where Node's `path.join` resolves `\` as a path separator). - The application passes a relative request URL (such as `req.url` or `req.originalUrl` without origin) into `CommonEngine.render({ url })`. - A sibling directory exists whose name starts with the same prefix as the configured `publicPath` directory (e.g., `dist\app-admin` alongside `dist\app`). - The targeted sibling directory contains prerendered HTML output containing the Angular SSG marker. ### Affected Versions - `>= 22.0.0, < 22.1.7` - `>= 21.0.0, < 21.2.23` - `>= 20.0.0, < 20.3.36` - `<= 19.2.27` ### Patches - `22.1.7` - `21.2.23` - `20.3.36` > Versions `<= 19.2.27` have reached End of Support / LTS expiration and will not be patched. ### Workarounds Until 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: ```ts server.use((req, res, next) => { const { protocol, originalUrl, headers } = req; // Normalize backslashes or construct a full HTTP URL (which forces WHATWG URL normalization) const sanitizedUrl = `${protocol}://${headers.host}${originalUrl.replace(/\\/g, '/')}`; commonEngine .render({ bootstrap, documentFilePath: indexHtml, url: sanitizedUrl, publicPath: distFolder, }) .then((html) => res.send(html)) .catch((err) => next(err)); }); ``` Alternatively, migrate from the deprecated `CommonEngine` to `AngularNodeAppEngine`, which relies on manifest-based route matching rather than direct filesystem path resolution.

Source published

5 Oct 2026 22:53:45 UTC

Source modified

5 Oct 2026 23:00:04 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · 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

Publisher rating · MODERATE