CVE-2026-72583 fastschema - Stored Cross-Site Scripting via MIME Type Bypass in File Upload
A low-privileged user can execute arbitrary JavaScript in other users' browsers by uploading a malicious SVG file that bypasses MIME type checks.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-72583?
CVE-2026-72583 is a medium-severity cross-site scripting vulnerability in fastschema, published on 10 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
A stored cross-site scripting (XSS) vulnerability in fastschema through v0.15.1 allows a low-privileged authenticated user to upload an SVG file containing malicious JavaScript by bypassing the MIME type allow-list check.
Weakness: CWE-79
Which versions are affected by CVE-2026-72583?
How do I fix CVE-2026-72583?
No fix has been published for CVE-2026-72583 yet. Limit exposure of the affected software until one is available.
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-2026-72583 being exploited?
There is no known exploitation of CVE-2026-72583 in the wild and no public exploit code.
Sources
Also known as GHSA-6vrh-w6p3-v6fh.