CVE-2026-18736

Received Received - Intake

Shlink SSRF via Title Auto-Resolution in Short URL Creation

Publication date: 2026-08-03

Last updated on: 2026-08-03

Assigner: VulnCheck

Description

Shlink contains a server-side request forgery vulnerability that allows authenticated API key holders to cause the server to issue arbitrary HTTP GET requests by supplying a crafted long URL during short URL creation with title auto-resolution enabled. Attackers can submit URLs pointing to public hosts that redirect to internal targets, including loopback addresses, link-local ranges, and cloud metadata endpoints such as 169.254.169.254, to exfiltrate internal service information via the HTML title element returned in the short URL creation response.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-03

Last Modified

2026-08-03

Generated

2026-08-04

AI Q&A

2026-08-04

EPSS Evaluated

N/A

NVD

CVE-2026-18736

EUVD

EUVD-2026-52427

Affected Vendors & Products

Vendor	Product	Version / Range
shlink	shlink	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-918	The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

Attack-Flow Graph

Executive Summary

Shlink has a server-side request forgery (SSRF) vulnerability. Authenticated API key holders can trick the server into making arbitrary HTTP GET requests by providing a specially crafted long URL during short URL creation when title auto-resolution is enabled. Attackers can use this to redirect requests to internal services or cloud metadata endpoints like 169.254.169.254 to steal internal service information via the HTML title in the response.

Detection Guidance

Detecting this SSRF vulnerability in Shlink requires monitoring for unusual HTTP requests to internal or sensitive endpoints during short URL creation. Check Shlink server logs for requests to loopback addresses (127.0.0.1, ::1), link-local ranges (169.254.0.0/16), or cloud metadata endpoints (169.254.169.254). Look for patterns where the server fetches titles from crafted URLs with auto-resolution enabled.

Impact Analysis

If you use Shlink with API key authentication and title auto-resolution enabled, an attacker with your API key could exfiltrate internal network information or access restricted services. This could lead to data leaks, unauthorized access to internal systems, or further attacks on your infrastructure.

Compliance Impact

This vulnerability could violate compliance requirements like GDPR (data protection) or HIPAA (health data privacy) by enabling unauthorized access to internal systems or data exfiltration. Organizations may face penalties or legal consequences if such breaches occur due to inadequate security measures.

Mitigation Strategies

Disable title auto-resolution during short URL creation in Shlink to prevent SSRF via crafted URLs. Restrict API key access to trusted users only and monitor for unusual HTTP requests to internal or loopback addresses.

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