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CVE-2026-40487

Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS

Published: Apr 18, 2026Updated: Apr 18, 2026 Sources: CVE List NVD
NVD MITRE
8.9CVSS
HIGH

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.

EPSS Score
N/A
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available

CVSS Vector Breakdown

AV:NAC:LPR:LUI:RS:CC:HI:HA:L
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:RUser Interaction
Required
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:LAvailability
Low

Weaknesses

CWE-79CWE-345CWE-434

Affected Products

postiz-app
gitroomhq

Attack Graph

Products CVE Techniques Tactics

Click technique nodes to view MITRE ATT&CK details. Scroll to zoom, drag to pan.

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

MITRE ATT&CK

6 techniques
Collection
Command and Control
Execution
Initial Access
Persistence
View detailed technique mapping

References

https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6
github.com
https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx
github.com

Timeline

Published
Apr 18, 2026
Last Updated
Apr 18, 2026

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