Angular: Angular SSR Request Vulnerability Allows Attackers to Trick Applications into Sending Unauthorized Requests

Critical SSRF Vulnerability in Angular SSR Exposes Web Applications to Attack

A severe Server-Side Request Forgery (SSRF) vulnerability, tracked as CVE-2026-27739, has been discovered in Angular’s Server-Side Rendering (SSR) framework. The flaw allows attackers to manipulate HTTP headers and redirect application requests to malicious domains, posing significant risks to affected web applications.

Root Cause & Exploitation

The vulnerability stems from Angular SSR’s insecure handling of user-controlled HTTP headers, particularly the Host and X-Forwarded-* headers. The framework fails to validate whether these headers originate from a trusted source, enabling attackers to:

• Manipulate the base origin of the application, causing HttpClient to resolve URLs to attacker-controlled servers.
• Construct malformed URIs by injecting non-numeric values into the X-Forwarded-Port header or unsanitized path segments into X-Forwarded-Host.

Successful exploitation could lead to:

• Credential exfiltration (e.g., Authorization headers, session cookies).
• Internal network probing, allowing access to private services, databases, or cloud metadata endpoints.
• Data breaches, exposing sensitive server-side information.

Affected Versions & Mitigation

The Angular team has released patched versions to address the flaw:

• 21.2.0-rc.1
• 21.1.5
• 20.3.17
• 19.2.21

For organizations unable to upgrade immediately, workarounds include:

• Avoiding req.headers for URL construction in favor of absolute, trusted base URLs.
• Implementing strict header validation middleware in server.ts to enforce numeric ports and validated hostnames.

The advisory, published on GitHub, underscores the urgency of applying fixes to prevent exploitation.

Source: https://cybersecuritynews.com/angular-ssr-request-vulnerability/

Angular cybersecurity rating report: https://www.rankiteo.com/company/angularframework

"id": "ANG1772447096",
"linkid": "angularframework",
"type": "Vulnerability",
"date": "3/2026",
"severity": "85",
"impact": "4",
"explanation": "Attack with significant impact with customers data leaks"

{'affected_entities': [{'customers_affected': 'Web applications using affected '
                                              'Angular SSR versions',
                        'industry': 'Technology/Software Development',
                        'name': 'Angular SSR Framework',
                        'type': 'Software Framework'}],
 'attack_vector': 'Manipulation of HTTP headers (Host, X-Forwarded-*)',
 'data_breach': {'data_exfiltration': 'Possible',
                 'sensitivity_of_data': 'High',
                 'type_of_data_compromised': ['Credentials (Authorization '
                                              'headers, session cookies)',
                                              'Sensitive server-side '
                                              'information']},
 'description': 'A severe Server-Side Request Forgery (SSRF) vulnerability, '
                'tracked as CVE-2026-27739, has been discovered in Angular’s '
                'Server-Side Rendering (SSR) framework. The flaw allows '
                'attackers to manipulate HTTP headers and redirect application '
                'requests to malicious domains, posing significant risks to '
                'affected web applications.',
 'impact': {'data_compromised': 'Sensitive server-side information, '
                                'credentials (Authorization headers, session '
                                'cookies)',
            'operational_impact': 'Internal network probing, access to private '
                                  'services/databases/cloud metadata endpoints',
            'systems_affected': 'Web applications using Angular SSR'},
 'lessons_learned': 'Importance of strict header validation and avoiding '
                    'user-controlled inputs for URL construction in '
                    'server-side frameworks',
 'post_incident_analysis': {'corrective_actions': 'Patch release, header '
                                                  'validation middleware, and '
                                                  'secure URL construction '
                                                  'practices',
                            'root_causes': 'Insecure handling of '
                                           'user-controlled HTTP headers '
                                           '(Host, X-Forwarded-*) in Angular '
                                           'SSR'},
 'recommendations': ['Upgrade to patched Angular SSR versions immediately',
                     'Implement strict header validation middleware in '
                     '`server.ts`',
                     'Use absolute, trusted base URLs instead of `req.headers` '
                     'for URL resolution'],
 'references': [{'source': 'GitHub Advisory'}],
 'response': {'containment_measures': 'Avoid using `req.headers` for URL '
                                      'construction; use absolute, trusted '
                                      'base URLs',
              'remediation_measures': 'Upgrade to patched versions '
                                      '(21.2.0-rc.1, 21.1.5, 20.3.17, '
                                      '19.2.21)'},
 'title': 'Critical SSRF Vulnerability in Angular SSR Exposes Web Applications '
          'to Attack',
 'type': 'SSRF (Server-Side Request Forgery)',
 'vulnerability_exploited': 'CVE-2026-27739'}