{"cve":"CVE-2026-33397","nvd":{"published":"2026-03-26T15:16:38.533","modified":"2026-06-17T10:37:25.300","status":"Analyzed","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_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","score":6.9},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","score":6.1},"cwes":["CWE-601"],"references":["https://github.com/advisories/GHSA-xh43-g2fq-wjrj","https://github.com/angular/angular-cli/pull/32771","https://github.com/angular/angular-cli/security/advisories/GHSA-vfx2-hv2g-xj5f"],"products":["angular:angular_cli"],"source":"nvd","synced_at":"2026-10-19T22:28:18.033120106+00:00"},"epss":{"cve":"CVE-2026-33397","score":0.0026,"percentile":0.17774,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-vfx2-hv2g-xj5f","url":"https://osv.dev/vulnerability/GHSA-vfx2-hv2g-xj5f","summary":"Protocol-Relative URL Injection via Single Backslash Bypass in Angular SSR","modified":"2026-05-06T20:48:57.282773Z","packages":[{"ecosystem":"npm","name":"@angular/ssr","purl":"pkg:npm/%40angular/ssr","ranges":[">=22.0.0-next.0 <22.0.0-next.2"],"fixed":["22.0.0-next.2"]},{"ecosystem":"npm","name":"@angular/ssr","purl":"pkg:npm/%40angular/ssr","ranges":[">=21.0.0-next.0 <21.2.3"],"fixed":["21.2.3"]},{"ecosystem":"npm","name":"@angular/ssr","purl":"pkg:npm/%40angular/ssr","ranges":[">=20.0.0-next.0 <20.3.21"],"fixed":["20.3.21"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}