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Medium, CVSS 6.3amended

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

CVE-2026-104871GHSA-7g7c-h8rr-7p6q

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm @angular/ssr

    Affected
    >= 22.0.0, < 22.1.7>= 21.0.0, < 21.2.23>= 20.0.0, < 20.3.36<= 19.2.27
    Fixed in
    20.3.36, 22.1.7, 21.2.23

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
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 · score source
EPSS
  • CVE-2026-104871: 0.42% estimated exploitation activity in the next 30 days; percentile 36.51 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-7g7c-h8rr-7p6q

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GHSA-7g7c-h8rr-7p6q

  4. Revision 1 · created ·

    Published from ghsa record GHSA-7g7c-h8rr-7p6q

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-104871

Advisory: Angular SSR: Path Traversal to Sibling Directories in CommonEngine on Windows
IDs: CVE-2026-104871, GHSA-7g7c-h8rr-7p6q
Record: https://patchnext.com/advisories/cve-2026-104871 (revision 4, source checked 26 Oct 2026, 13:06 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: @angular/ssr 22.1.7, 21.2.23, 20.3.36. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @angular/ssr: affected >= 22.0.0, < 22.1.7; >= 21.0.0, < 21.2.23; >= 20.0.0, < 20.3.36; <= 19.2.27; fixed in 20.3.36, 22.1.7, 21.2.23

## Suggested inspection (read-only)
- `npm ls @angular/ssr --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @angular/ssr.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-7g7c-h8rr-7p6q (GitHub-reviewed advisory GHSA-7g7c-h8rr-7p6q lists affected ranges: npm @angular/ssr >=22.0.0 =21.0.0 =20.0.0 =0 <=19.2.27)
- Verified: https://osv.dev/vulnerability/GHSA-7g7c-h8rr-7p6q (OSV record GHSA-7g7c-h8rr-7p6q lists affected ranges: npm @angular/ssr >=22.0.0 =21.0.0 =20.0.0 =0 <=19.2.27)

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