CVE-2026-40487
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.22%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 9.0 CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
- EPSS
- 0.22% probability · 13th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-79, CWE-345, CWE-434
- Affected
- gitroom/postiz
- Source
- security-advisories@github.com
References
- https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6Product, Release Notes
- https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfxExploit, Vendor Advisory
- https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfxExploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.