XSS in Zmievsa Cadwyn

CVE-2025-53528

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:L.

EPSS exploit prediction

EPSS: 0.002 (14.2th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 14th percentile — 14.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2025-53528: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2025-53528?
CVE-2025-53528 is a high-severity vulnerability in Zmievsa Cadwyn, classified under Cross-site Scripting. CVSS score: 7.6/10. Published 2025-07-21.
How severe is CVE-2025-53528?
High severity. CVSS v3 base score is 7.6 out of 10.