# CVE-2026-27738: Angular SSR has an Open Redirect via X-Forwarded-Prefix

> Attackers can exploit improper URL normalization in Angular SSR to perform open redirects, enabling phishing and SEO hijacking when specific proxy headers are used.

- **Severity:** Medium 6.9 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Feb 2026
- **Updated:** 27 Feb 2026
- **Also known as:** GHSA-xh43-g2fq-wjrj

## What is CVE-2026-27738?

CVE-2026-27738 is a medium-severity vulnerability in angular-cli, published on 25 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2026-27738?

8 open source packages ship an affected version, including @angular/ssr.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@angular/ssr` | npm | From 19.0.0-next.0 | 19.2.21 |
| `@angular/ssr` | npm | From 19.0.0-next.0 | 19.2.21 |
| `@angular/ssr` | npm | From 20.0.0-next.0 | 20.3.17 |
| `@angular/ssr` | npm | From 20.0.0-next.0 | 20.3.17 |
| `@angular/ssr` | npm | From 21.0.0-next.0 | 21.1.5 |
| `@angular/ssr` | npm | From 21.0.0-next.0 | 21.1.5 |
| `@angular/ssr` | npm | From 21.2.0-next.0 | 21.2.0-rc.1 |
| `@angular/ssr` | npm | From 21.2.0-next.0 | 21.2.0-rc.1 |

## How do I fix CVE-2026-27738?

Upgrade @angular/ssr to a fixed version for your release line: 19.2.21, 20.3.17, 21.1.5 or 21.2.0-rc.1.

## Is CVE-2026-27738 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27738 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27738 and fix it if it is affected.

What it is: CVE-2026-27738 is a medium-severity vulnerability in angular-cli, published on 25 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27738 exists.

Affected packages and fixed versions:
- @angular/ssr (npm): affected from 19.0.0-next.0; fixed in 19.2.21
- @angular/ssr (npm): affected from 19.0.0-next.0; fixed in 19.2.21
- @angular/ssr (npm): affected from 20.0.0-next.0; fixed in 20.3.17
- @angular/ssr (npm): affected from 20.0.0-next.0; fixed in 20.3.17
- @angular/ssr (npm): affected from 21.0.0-next.0; fixed in 21.1.5
- @angular/ssr (npm): affected from 21.0.0-next.0; fixed in 21.1.5
- @angular/ssr (npm): affected from 21.2.0-next.0; fixed in 21.2.0-rc.1
- @angular/ssr (npm): affected from 21.2.0-next.0; fixed in 21.2.0-rc.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27738/ (Markdown: https://insights.sbomify.com/CVE-2026-27738/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27738
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27738
- OSV: https://osv.dev/vulnerability/CVE-2026-27738

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27738/
Summaries are generated and may contain mistakes; the official description above is the record.