CVE-2026-18736

Shlink Server-Side Request Forgery via Short URL Title Auto-Resolution

Published Aug 3, 2026 CVSS 4.0 · 5.3 Medium EPSS < 1% KEV · Not listed

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.

Analysis

Technical impact

Shlink contains a server‑side request forgery vulnerability that allows holders of an authenticated API key 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. The attacker can target external hosts that redirect to internal or loopback addresses, link‑local ranges, or cloud metadata endpoints such as 169.254.169.254, and exfiltrate internal service information via the HTML title element returned in the short URL creation response.

Affected Systems

The affected system is the Shlink platform supplied by shlinkio. No specific version information is provided in the advisory, so all versions hosted by shlinkio may be impacted until a patch is released.

Risk and Exploitability

The CVSS score of 5.3 indicates a moderate severity. EPSS is not available and the vulnerability is not listed in the CISA KEV catalog. The attack vector is inferred to be through authenticated API usage; an attacker with an API key can submit a malicious URL that forces the server to contact internal resources, potentially exposing confidential data. The lack of available EPSS data means the exploitation probability is unknown, but the presence of an authentication requirement mitigates the immediate risk to unauthenticated users.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

shlinkio

Shlink

affected

Version	Status	Constraints
`2.6.0`	affected	≤ 5.1.5

No data.

Vendor Product Versions

Shlink

Version	Status	Scheme	Platform
`[2.6.0,5.1.5]`	affected	semver	—

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Upgrade to a patched Shlink version that addresses the SSRF issue.
Disable the title auto‑resolution feature in the API configuration.
Restrict API key permissions and monitor API usage for suspicious redirects.

Generated by OpenCVE AI on August 4, 2026 at 09:48 UTC.

Tracking

Advisories

No advisories available

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact Low

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Scope Changed

Confidentiality Impact Low

Integrity Impact None

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.331% probability within 30 days)

Exploitation poc

Automatable no

Technical Impact partial

References

Link	Providers
https://github.com/shlinkio/shlink
https://github.com/theopaid/Server-side-request-forgery-through-short-URL-title-resolution-shlink-
https://www.vulncheck.com/advisories/shlink-server-side-request-forgery-via-short-url-title-auto-resolution

History

Aug 5, 2026 10:00 AM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Shlink Shlink shlink
Vendors & Products		Shlink Shlink shlink

Aug 4, 2026 2:30 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Aug 3, 2026 8:45 PM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
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.
Title		Shlink Server-Side Request Forgery via Short URL Title Auto-Resolution
Weaknesses		CWE-918
References		https://github.com/shlinkio/shlink https://github.com/theopaid/Server-side-request-forgery-through-short-URL-title-resolution-shlink- https://www.vulncheck.com/advisories/shlink-server-side-request-forgery-via-short-url-title-auto-resolution
Metrics		cvssV3_1 `{'score': 5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N'}` cvssV4_0 `{'score': 5.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N'}`