Vulnerability-Lookup

GHSA-XH43-G2FQ-WJRJ

Vulnerability from github – Published: 2026-02-25 22:41 – Updated: 2026-02-25 22:41

Summary

Angular SSR has an Open Redirect via X-Forwarded-Prefix

Details

An Open Redirect vulnerability exists in the internal URL processing logic in Angular SSR. The logic normalizes URL segments by stripping leading slashes; however, it only removes a single leading slash.

When an Angular SSR application is deployed behind a proxy that passes the X-Forwarded-Prefix header, an attacker can provide a value starting with three slashes (e.g., ///evil.com).

The application processes a redirect (e.g., from a router redirectTo or i18n locale switch).
Angular receives ///evil.com as the prefix.
It strips one slash, leaving //evil.com.
The resulting string is used in the Location header.
Modern browsers interpret // as a protocol-relative URL, redirecting the user from https://your-app.com to https://evil.com.

Impact

This vulnerability allows attackers to conduct large-scale phishing and SEO hijacking: - Scale: A single request can poison a high-traffic route, impacting all users until the cache expires. - SEO Poisoning: Search engine crawlers may follow and index these malicious redirects, causing the legitimate site to be delisted or associated with malicious domains. - Trust: Because the initial URL belongs to the trusted domain, users and security tools are less likely to flag the redirect as malicious.

Attack Preconditions

The application must use Angular SSR.
The application must have routes that perform internal redirects.
The infrastructure (Reverse Proxy/CDN) must pass the X-Forwarded-Prefix header to the SSR process without sanitization.
The cache must not vary on the X-Forwarded-Prefix header.

Patches

21.2.0-rc.1
21.1.5
20.3.17
19.2.21

Workarounds

Until the patch is applied, developers should sanitize the X-Forwarded-Prefix header in theirserver.ts before the Angular engine processes the request:

app.use((req, res, next) => {
  const prefix = req.headers['x-forwarded-prefix']?.trim();
  if (prefix) {
    // Sanitize by removing all leading slashes
    req.headers['x-forwarded-prefix'] = prefix.replace(/^[/\\]+/, '/');
  }
  next();
});

Resources

Report
Fix

Severity

6.9 (Medium)


                  
                    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

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JSON

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c 21.2.0-rc.0"
      },
      "package": {
        "ecosystem": "npm",
        "name": "@angular/ssr"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "21.2.0-next.0"
            },
            {
              "fixed": "21.2.0-rc.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@angular/ssr"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "21.0.0-next.0"
            },
            {
              "fixed": "21.1.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@angular/ssr"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "20.0.0-next.0"
            },
            {
              "fixed": "20.3.17"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@angular/ssr"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "19.0.0-next.0"
            },
            {
              "fixed": "19.2.21"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27738"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-601"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-25T22:41:57Z",
    "nvd_published_at": "2026-02-25T17:25:40Z",
    "severity": "MODERATE"
  },
  "details": "An Open Redirect vulnerability exists in the internal URL processing logic in Angular SSR. The logic normalizes URL segments by stripping leading slashes; however, it only removes a single leading slash.\n\nWhen an Angular SSR application is deployed behind a proxy that passes the `X-Forwarded-Prefix` header, an attacker can provide a value starting with three slashes (e.g., `///evil.com`).\n\n1. The application processes a redirect (e.g., from a router `redirectTo` or i18n locale switch).\n2. Angular receives `///evil.com` as the prefix.\n3. It strips one slash, leaving `//evil.com`.\n4. The resulting string is used in the `Location` header.\n5. Modern browsers interpret `//` as a protocol-relative URL, redirecting the user from `https://your-app.com` to `https://evil.com`.\n\n\n### Impact\nThis vulnerability allows attackers to conduct large-scale phishing and SEO hijacking:\n- **Scale:** A single request can poison a high-traffic route, impacting all users until the cache expires.\n- **SEO Poisoning:** Search engine crawlers may follow and index these malicious redirects, causing the legitimate site to be delisted or associated with malicious domains.\n- **Trust:** Because the initial URL belongs to the trusted domain, users and security tools are less likely to flag the redirect as malicious.\n\n### Attack Preconditions\n\n- The application must use Angular SSR.\n- The application must have routes that perform internal redirects.\n- The infrastructure (Reverse Proxy/CDN) must pass the `X-Forwarded-Prefix` header to the SSR process without sanitization.\n- The cache must not vary on the `X-Forwarded-Prefix` header.\n\n### Patches\n- 21.2.0-rc.1\n- 21.1.5\n- 20.3.17\n- 19.2.21\n\n### Workarounds\nUntil the patch is applied, developers should sanitize the `X-Forwarded-Prefix` header in their`server.ts` before the Angular engine processes the request:\n\n```ts\napp.use((req, res, next) =\u003e {\n  const prefix = req.headers[\u0027x-forwarded-prefix\u0027]?.trim();\n  if (prefix) {\n    // Sanitize by removing all leading slashes\n    req.headers[\u0027x-forwarded-prefix\u0027] = prefix.replace(/^[/\\\\]+/, \u0027/\u0027);\n  }\n  next();\n});\n\n```\n\n### Resources\n- [Report](https://github.com/angular/angular-cli/issues/32501)\n- [Fix](https://github.com/angular/angular-cli/pull/32521)",
  "id": "GHSA-xh43-g2fq-wjrj",
  "modified": "2026-02-25T22:41:57Z",
  "published": "2026-02-25T22:41:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/angular/angular-cli/security/advisories/GHSA-xh43-g2fq-wjrj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27738"
    },
    {
      "type": "WEB",
      "url": "https://github.com/angular/angular-cli/issues/32501"
    },
    {
      "type": "WEB",
      "url": "https://github.com/angular/angular-cli/pull/32521"
    },
    {
      "type": "WEB",
      "url": "https://github.com/angular/angular-cli/commit/f086eccc36d10cf01c426e35864bc32e1e292323"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/angular/angular-cli"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Angular SSR has an Open Redirect via X-Forwarded-Prefix"
}

CVE-2026-27738 (GCVE-0-2026-27738)

Vulnerability from cvelistv5 – Published: 2026-02-25 16:40 – Updated: 2026-02-27 20:46

Title

Angular SSR has an Open Redirect via X-Forwarded-Prefix

Summary

The Angular SSR is a server-rise rendering tool for Angular applications. An Open Redirect vulnerability exists in the internal URL processing logic in versions on the 19.x branch prior to 19.2.21, the 20.x branch prior to 20.3.17, and the 21.x branch prior to 21.1.5 and 21.2.0-rc.1. The logic normalizes URL segments by stripping leading slashes; however, it only removes a single leading slash. When an Angular SSR application is deployed behind a proxy that passes the `X-Forwarded-Prefix` header, an attacker can provide a value starting with three slashes. This vulnerability allows attackers to conduct large-scale phishing and SEO hijacking. In order to be vulnerable, the application must use Angular SSR, the application must have routes that perform internal redirects, the infrastructure (Reverse Proxy/CDN) must pass the `X-Forwarded-Prefix` header to the SSR process without sanitization, and the cache must not vary on the `X-Forwarded-Prefix` header. Versions 21.2.0-rc.1, 21.1.5, 20.3.17, and 19.2.21 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.

Severity

6.9 (Medium)


                        
                          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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-02-27 20:46 UTC

CWE

CWE-601 - URL Redirection to Untrusted Site ('Open Redirect')

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/angular/angular-cli/security/a…	x_refsource_CONFIRM
https://github.com/angular/angular-cli/issues/32501	x_refsource_MISC
https://github.com/angular/angular-cli/pull/32521	x_refsource_MISC
https://github.com/angular/angular-cli/commit/877…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
angular	angular-cli	Affected: >= 21.2.0-next.2, < 21.2.0-rc.0 Affected: >= 21.0.0-next.0, < 21.1.5 Affected: >= 20.0.0-next.0, < 20.3.17 Affected: >= 19.0.0-next.0, < 19.2.21

Show details on NVD website

JSON

To clipboard

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  "containers": {
    "adp": [
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        "metrics": [
          {
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                "id": "CVE-2026-27738",
                "options": [
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                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-02-27T20:46:21.327125Z",
                "version": "2.0.3"
              },
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        "providerMetadata": {
          "dateUpdated": "2026-02-27T20:46:26.917Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
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          {
            "tags": [
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    "cna": {
      "affected": [
        {
          "product": "angular-cli",
          "vendor": "angular",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 21.2.0-next.2, \u003c 21.2.0-rc.0"
            },
            {
              "status": "affected",
              "version": "\u003e= 21.0.0-next.0, \u003c 21.1.5"
            },
            {
              "status": "affected",
              "version": "\u003e= 20.0.0-next.0, \u003c 20.3.17"
            },
            {
              "status": "affected",
              "version": "\u003e= 19.0.0-next.0, \u003c 19.2.21"
            }
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "The Angular SSR is a server-rise rendering tool for Angular applications. An Open Redirect vulnerability exists in the internal URL processing logic in versions on the 19.x branch prior to 19.2.21, the 20.x branch prior to 20.3.17, and the 21.x branch prior to 21.1.5 and 21.2.0-rc.1. The logic normalizes URL segments by stripping leading slashes; however, it only removes a single leading slash. When an Angular SSR application is deployed behind a proxy that passes the `X-Forwarded-Prefix` header, an attacker can provide a value starting with three slashes. This vulnerability allows attackers to conduct large-scale phishing and SEO hijacking. In order to be vulnerable, the application must use Angular SSR, the application must have routes that perform internal redirects, the infrastructure (Reverse Proxy/CDN) must pass the `X-Forwarded-Prefix` header to the SSR process without sanitization, and the cache must not vary on the `X-Forwarded-Prefix` header. Versions 21.2.0-rc.1, 21.1.5, 20.3.17, and 19.2.21 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."
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      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

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