CVE-2026-33397
Versions on the 22.x branch prior to 22.0.0-next.2, the 21.x branch prior to 21.2.3, and the 20.x branch prior to 20.3.21 have an Open Redirect vulnerability in `@angular/ssr` due to an incomplete fix for CVE-2026-27738.
Does this matter?
Lower severity and a low EPSS score (0.26%). Track it; it rarely justifies an emergency change on its own.
Description
The Angular SSR is a server-rise rendering tool for Angular applications. Versions on the 22.x branch prior to 22.0.0-next.2, the 21.x branch prior to 21.2.3, and the 20.x branch prior to 20.3.21 have an Open Redirect vulnerability in `@angular/ssr` due to an incomplete fix for CVE-2026-27738. While the original fix successfully blocked multiple leading slashes (e.g., `///`), the internal validation logic fails to account for a single backslash (`\`) bypass. When an Angular SSR application is deployed behind a proxy that passes the `X-Forwarded-Prefix` header, an attacker provides a value starting with a single backslash, the internal validation failed to flag the single backslash as invalid, the application prepends a leading forward slash, resulting in a `Location` header containing the URL, and modern browsers interpret the `/\` sequence as `//`, treating it as a protocol-relative URL and redirecting the user to the attacker-controlled domain. Furthermore, the response lacks the `Vary: X-Forwarded-Prefix` header, allowing the malicious redirect to be stored in intermediate caches (Web Cache Poisoning). Versions 22.0.0-next.2, 21.2.3, and 20.3.21 contain a patch. Until the patch is applied, developers should sanitize the `X-Forwarded-Prefix` header in their `server.ts` before the Angular engine processes the request.
- CVSS 4.0
- 6.9 MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.26% probability · 17th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-601
- Affected
- angular/angular cli
- Source
- security-advisories@github.com
References
- https://github.com/advisories/GHSA-xh43-g2fq-wjrjNot Applicable
- https://github.com/angular/angular-cli/pull/32771Issue Tracking, Patch
- https://github.com/angular/angular-cli/security/advisories/GHSA-vfx2-hv2g-xj5fVendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.