by Kastro
Paper/Archive/CVE-2026-40487

CVE-2026-40487

gitroomhq postiz-app — Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS

EPSS 0.2%public exploitCVSS 9.0
critical.is priorityof 100
40
CVSS 9.0 (NVD)9.0 / 10 × 3027.0Not in CISA KEV+300.0EPSS percentile 13.1.131 × 202.6Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
postiz-app< 2.21.6–CNA

Scores by source

NVD9.0CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
GitHub_M (CNA)8.9CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L
CISA ADPSSVCExploitation: poc · Automatable: no · Technical impact: total

References

exploitgithub.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfxrefgithub.com/gitroomhq/postiz-app/releases/tag/v2.21.6