File Upload Validation Bypass in Postiz AI Social Media Tool
CVE-2026-40487

8.9HIGH

Key Information:

Vendor

Gitroomhq

Status
Postiz-app
Vendor
CVE Published:
18 April 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-40487?

Prior to version 2.21.6, the Postiz AI social media scheduling tool contained a vulnerability that allowed authenticated users to exploit a file upload validation bypass. By manipulating the Content-Type header, it became possible for users to upload potentially harmful files, such as HTML and SVG, to the server. These files were served with an appropriate Content-Type based on their extensions, which could subsequently lead to Stored Cross-Site Scripting (XSS) attacks. This vulnerability poses serious risks, including session riding and unauthorized account access, jeopardizing the security and privacy of users within the application.

Affected Version(s)

postiz-app < 2.21.6

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-40487
Created by Astaruf

References

https://github.com/gitroomhq/postiz-app/security/advisori...
x_refsource_CONFIRM
https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6
x_refsource_MISC

CVSS V3.1

Score:
8.9
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
Required
Scope:
Changed

Timeline

  • Vulnerability published

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability Reserved

.