CVE-2026-40487
Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS
CRITICAL 9.0EPSS 0.3%
Postiz is an AI social media scheduling tool. Prior to version 2.21.6, a file upload validation bypass allows any authenticated user to upload arbitrary HTML, SVG, or other executable file types to the server by spoofing the `Content-Type` header. The uploaded files are then served by nginx with a Content-Type derived from their original extension (`text/html`, `image/svg+xml`), enabling Stored Cross-Site Scripting (XSS) in the context of the application's origin. This can lead to session riding, account takeover, and full compromise of other users' accounts. Version 2.21.6 contains a fix.
- Affected
- gitroomhq · postiz-app
- CVSS v3.1 NVD
- 9.0 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H - CVSS v3.1 GITHUB
- 8.9 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L - EPSS
- 0.26% chance of exploitation in the next 30 days, 16th percentile
- Published
- 2026-04-18
- Updated
- 2026-04-20
Proof-of-concept exploits (1)
- Astaruf/CVE-2026-404873★ · 2026-04-22
Security advisories
- gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx
- gitroomhq/postiz-app/releases/tag/v2.21.6