Angular SSR: Open Redirect and Request Steering via Encoded X-Forwarded-Prefix

Summary

The Angular SSR is a server-rise rendering tool for Angular applications. From 19.0.0-next.0 to before 19.2.25, 20.3.25, 21.2.9, and 22.0.0-next.7, a vulnerability exists in the X-Forwarded-Prefix header processing logic within Angular SSR. The internal validation mechanism fails to properly account for URL-encoded characters, specifically dots (%2e%2e). This allows an attacker to bypass security filters by injecting encoded path traversal sequences that are later decoded and utilized by the application logic. When an Angular SSR application is configured to trust proxy headers and is deployed behind a proxy that forwards the X-Forwarded-Prefix header without prior sanitization, an attacker can provide a payload such as /%2e%2e/evil. This vulnerability is fixed in19.2.25, 20.3.25, 21.2.9, and 22.0.0-next.7.

Timeline

1. May 13, 2026, 9:23 PM UTCCVE published
2. May 14, 2026, 1:33 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. May 14, 2026, 1:35 PM UTCRecord last updated

Affected versions

• angular angular-cli

  From 22.0.0-next.0 · fixed in 22.0.0-next.7; From 21.0.0-next.0 · fixed in 21.2.9; From 20.0.0-next.0 · fixed in 20.3.25; From 19.0.0-next.0 · fixed in 19.2.25

• @angular/ssrnpm

  From 22.0.0-next.0 · fixed in 22.0.0-next.7

• @angular/ssrnpm

  From 21.0.0-next.0 · fixed in 21.2.9

• @angular/ssrnpm

  From 20.0.0-next.0 · fixed in 20.3.25

• @angular/ssrnpm

  From 19.0.0-next.0 · fixed in 19.2.25

References 2