Angular SSR Vulnerability Exposes Sensitive Data to Attackers

A newly discovered high-severity vulnerability (CVE-2025-59052) in Angular’s server-side rendering (SSR) feature puts user data at risk by allowing attackers to access information from other sessions during high-concurrency operations.

Organizations using Angular’s SSR should act quickly to implement fixes or recommended workarounds to prevent potential breaches.

Race Condition in SSR Platform Injector

The issue stems from a global race condition in the Angular SSR platform injector, responsible for storing request-specific data during rendering.

Historically, this container was implemented as a module-scoped global variable.

When multiple requests are processed simultaneously, the global injector state can be shared or overwritten, resulting in cross-request data leakage.

This vulnerability (CVSS 7.1, High) means that sensitive session data—such as authentication tokens, user settings, or database query results—meant for one user could inadvertently be returned to another.

Attackers with network access can exploit the flaw by sending repeated SSR requests and inspecting the responses for leaked session data.

The exploitation requires no special privileges or user interaction, making it a significant risk for high-traffic web applications.

The fix for CVE-2025-59052 introduces notable changes in Angular SSR server code:

• The bootstrapApplication function now requires a per-request BootstrapContext argument to ensure the correct injector is used.
• The getPlatform API has changed to always return null on the server, ensuring per-request isolation.
• The destroyPlatform function becomes a no-op during SSR.

Angular has released automatic update schematics for versions 18, 19, and 20, simplifying the migration process via the ng update command.

All active major release lines, including prereleases, have received patches.

Developers should upgrade to:

• @angular/platform-server 18.2.14, 19.2.15, 20.3.0, or 21.0.0-next.3
  and update related @angular/ssr and @nguniversal/common packages.

Until updates are deployed, teams can mitigate risk by:

• Disabling SSR via server routing or builder configuration.
• Removing asynchronous logic from custom bootstrap functions.
• Eliminating calls to getPlatform().
• Forcing JIT mode off in server builds.

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