CVE-2026-40487
Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS
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.
INFO
Published Date :
April 18, 2026, 2:16 a.m.
Last Modified :
April 23, 2026, 3:27 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | CRITICAL | [email protected] |
Solution
- Update Postiz to version 2.21.6 or later.
- Verify file upload validation is enforced.
- Remove any previously uploaded malicious files.
- Scan for any signs of account compromise.
Public PoC/Exploit Available at Github
CVE-2026-40487 has a 4 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40487.
| URL | Resource |
|---|---|
| https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6 | Product Release Notes |
| https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx | Exploit Vendor Advisory |
| https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40487 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40487
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
CVE-2026-40487
Python
CVE-2026-40487 - Postiz <= 2.21.5 - Arbitrary File Upload via MIME-Type Spoofing → Stored XSS → Account Takeover
account-takeover cve exploit file-upload mime-spoofing poc postiz security stored-xss vulnerability xss cve-2026-40487
Python
CVE POC repo 자동 수집기
Python
📡 PoC auto collect from GitHub. ⚠️ Be careful Malware.
security cve exploit poc vulnerability
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40487 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-40487 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 23, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:gitroom:postiz:*:*:*:*:*:*:*:* versions up to (excluding) 2.21.6 Added Reference Type GitHub, Inc.: https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx Types: Exploit, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Apr. 20, 2026
Action Type Old Value New Value Added Reference https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx -
New CVE Received by [email protected]
Apr. 18, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L Added CWE CWE-79 Added CWE CWE-345 Added CWE CWE-434 Added Reference https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6 Added Reference https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx