# CVE-2026-13603: SSRF with API key leak in pretix-oppwa

> Attackers can exploit improper URL validation to force server-side requests to arbitrary hosts, leaking API keys and accessing payment provider data.

- **Severity:** Critical 9.0 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Jul 2026
- **Updated:** 1 Jul 2026
- **Also known as:** GHSA-29fq-jc8m-8rq2

## What is CVE-2026-13603?

CVE-2026-13603 is a critical server-side request forgery vulnerability in pretix-oppwa, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The payment integration pretix-oppwa provides support 
for the payment providers VR Payment, Hobex, and potentially others 
based on Oppwa's technology. The integration of Oppwa, following their 
official documentation, includes a step where the user is redirected 
from the payment provider back to our system with a query parameter like
 ?resourcePath=/v1/checkouts/{checkoutId}/payment in the URL. Our system is then supposed to fetch the status of the transaction from the URL given by baseUrl + resourcePath.

Our plugin pretix-oppwa did so insecurely by 
concatenating the parameter form the URL to the base domain of the API 
without further validation and, critically, without a / at the end of the baseUrl. Therefore, an attacker could inject a resourcePath argument in a way that causes pretix to call a different
 server instead. Since the request includes the access token (API key) 
of the Oppwa account, this would leak the access token, giving access to
 data contained in the payment provider's system. This is fixed with the
 release today by strictly validating the given API URL.

After installing the update, we recommend asking your payment provider for a new access token and updating it in pretix.

Weakness: CWE-918 (Server-Side Request Forgery), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-13603?


## How do I fix CVE-2026-13603?

No fix has been published for CVE-2026-13603 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-13603 being exploited?

There is no known exploitation of CVE-2026-13603 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-13603 and fix it if it is affected.

What it is: CVE-2026-13603 is a critical server-side request forgery vulnerability in pretix-oppwa, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-13603 in the wild and no public exploit code.

Affected product: pretix-oppwa. 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-2026-13603/ (Markdown: https://insights.sbomify.com/CVE-2026-13603/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-13603
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-13603
- OSV: https://osv.dev/vulnerability/CVE-2026-13603

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-13603/
Summaries are generated and may contain mistakes; the official description above is the record.