CVE-2025-53528 Cadwyn is vulnerable to an XSS attack through its docs page
An attacker can execute arbitrary JavaScript in a user's session via a reflected XSS vulnerability in the Cadwyn library's docs endpoint.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2025-53528?
CVE-2025-53528 is a high-severity cross-site scripting vulnerability in zmievsa cadwyn, published on 21 Jul 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Cadwyn creates production-ready community-driven modern Stripe-like API versioning in FastAPI. In versions before 5.4.3, the version parameter of the "/docs" endpoint is vulnerable to a Reflected XSS (Cross-Site Scripting) attack. This XSS would notably allow an attacker to execute JavaScript code on a user's session for any application based on Cadwyn via a one-click attack. The vulnerability has been fixed in version 5.4.3.
Weakness: CWE-79
Which versions are affected by CVE-2025-53528?
3 open source packages ship an affected version, including cadwyn.
| Package | Affected | Fixed in |
|---|---|---|
cadwyn PyPI | All versions | 5.4.3 |
cadwyn PyPI | All versions | 5.4.3 |
cadwyn PyPI | All versions | 5.4.3 |
How do I fix CVE-2025-53528?
Upgrade cadwyn to 5.4.3 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2025-53528 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-53528 exists.
Sources
Also known as GHSA-2gxp-6r36-m97r, PYSEC-2025-71.