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

> Authenticated attackers can exploit SSRF in Shlink to access internal services and cloud metadata via crafted URLs during short link creation.

- **Severity:** Medium 5.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 3 Aug 2026
- **Updated:** 4 Aug 2026
- **Also known as:** GHSA-c6g4-pfhg-gvmp

## What is CVE-2026-18736?

CVE-2026-18736 is a medium-severity server-side request forgery vulnerability in shlinkio Shlink, published on 3 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-18736?


## How do I fix CVE-2026-18736?

No fix has been published for CVE-2026-18736 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-18736 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-18736 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18736 and fix it if it is affected.

What it is: CVE-2026-18736 is a medium-severity server-side request forgery vulnerability in shlinkio Shlink, published on 3 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-18736 exists.

Affected product: shlinkio Shlink. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-18736/ (Markdown: https://insights.sbomify.com/CVE-2026-18736/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18736
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18736
- OSV: https://osv.dev/vulnerability/CVE-2026-18736

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18736/
Summaries are generated and may contain mistakes; the official description above is the record.