CVE-2026-13603

CVE-2026-13603 is a critical-severity vulnerability with a CVSS 4.0 base score of 9.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

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.

Frequently asked questions

What is CVE-2026-13603?
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.
How severe is CVE-2026-13603?
CVE-2026-13603 has a CVSS 4.0 base score of 9.0, rated critical severity.
Is CVE-2026-13603 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-13603?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-13603 published?
CVE-2026-13603 was published on 2026-07-01 and last updated on 2026-07-02.

References

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