---
title: "CVE-2026-27739: Angular SSR is vulnerable to SSRF and Header Injection via request handling pipeline"
url: https://erroneo.us/security/cve/CVE-2026-27739/
description: "CVE-2026-27739 (@angular/ssr (npm)): The Angular SSR is a server-rise rendering tool for Angular applications. Versions prior to 21.2.0-rc.1, 21.1.5…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-02-25
date_modified: 2026-02-27
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-27739"
kev: false
cvss: 9.2
epss: 0.00527
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-27739: Angular SSR is vulnerable to SSRF and Header Injection via request handling pipeline

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.5% , percentile 44: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 44% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes @angular/ssr (npm) >= 21.2.0-next.0, < 21.2.0-rc.0, fixed in 21.2.0-rc.1 ; @angular/ssr (npm) >= 21.0.0-next.0, < 21.1.5, fixed in 21.1.5 ; @angular/ssr (npm) >= 20.0.0-next.0, < 20.3.17, fixed in 20.3.17 ; @angular/ssr (npm) < 19.2.21, fixed in 19.2.21 . Check your lockfile, including transitive dependencies.

## What it is

The Angular SSR is a server-rise rendering tool for Angular applications. Versions prior to 21.2.0-rc.1, 21.1.5, 20.3.17, and 19.2.21 have a Server-Side Request Forgery (SSRF) vulnerability in the Angular SSR request handling pipeline. The vulnerability exists because Angular’s internal URL reconstruction logic directly trusts and consumes user-controlled HTTP headers specifically the Host and X-Forwarded- family to determine the application's base origin without any validation of the destination domain. Specifically, the framework didn't have checks for the host domain, path and character sanitization, and port validation. This vulnerability manifests in two primary ways: implicit relative URL resolution and explicit manual construction. When successfully exploited, this vulnerability allows for arbitrary internal request steering. This can lead to credential exfiltration, internal network probing, and a confidentiality breach. In order to be vulnerable, the victim application must use Angular SSR (Server-Side Rendering), the application must perform HttpClient requests using relative URLs OR manually construct URLs using the unvalidated Host / X-Forwarded- headers using the REQUEST object, the application server must be reachable by an attacker who can influence these headers without strict validation from a front-facing proxy, and the infrastructure (Cloud, CDN, or Load Balancer) must not sanitize or validate incoming headers. Versions 21.2.0-rc.1, 21.1.5, 20.3.17, and 19.2.21 contain a patch. Some workarounds are available. Avoid using req.headers for URL construction. Instead, use trusted variables for base API paths. Those who cannot upgrade immediately should implement a middleware in their server.ts to enforce numeric ports and validated hostnames.

## Affected packages

- npm `@angular/ssr` >= 21.2.0-next.0, < 21.2.0-rc.0 → fixed: 21.2.0-rc.1
- npm `@angular/ssr` >= 21.0.0-next.0, < 21.1.5 → fixed: 21.1.5
- npm `@angular/ssr` >= 20.0.0-next.0, < 20.3.17 → fixed: 20.3.17
- npm `@angular/ssr` < 19.2.21 → fixed: 19.2.21
- npm `@nguniversal/common` <= 16.2.0 → fixed: none listed
- npm `@nguniversal/express-engine` <= 16.2.0 → fixed: none listed

## Affected products (CVE record)

- angular angular-cli: >= 21.2.0-next.2, < 21.2.0-rc.0, >= 21.0.0-next.0, < 21.1.5, >= 20.0.0-next.0, < 20.3.17, < 19.2.21
- angular @nguniversal/common: <= 16.2.0
- angular @nguniversal/express-engine: <= 16.2.0

## Severity

- GitHub_M CVSS 4.0: 9.2 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N`
- GitHub CVSS 4.0: 9.2 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 0.53% probability of exploitation activity in the next 30 days; percentile 44.

## Sources

- [GitHub Advisory GHSA-x288-3778-4hhx](https://github.com/advisories/GHSA-x288-3778-4hhx)
- [CVE.org record CVE-2026-27739](https://www.cve.org/CVERecord?id=CVE-2026-27739)
- [NVD entry CVE-2026-27739](https://nvd.nist.gov/vuln/detail/CVE-2026-27739)
- [github.com](https://github.com/angular/angular-cli/security/advisories/GHSA-x288-3778-4hhx)
- [github.com](https://github.com/angular/angular-cli/pull/32516)
- [angular.dev](https://angular.dev/best-practices/security#preventing-server-side-request-forgery-ssrf)
- [developer.mozilla.org](https://developer.mozilla.org/en-US/docs/Web/Security/Attacks/SSRF)

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Source page: https://erroneo.us/security/cve/CVE-2026-27739/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt