CVE-2026-40487
Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS
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.
- Record
CVE-2026-40487- CVSS 3.1
- 8.9 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L - Weakness
- CWE-79, CWE-345, CWE-434
- Updated
- 2026-11-02
EUVDEUVD-2026-23634
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.
- Record
EUVD-2026-23634- CVSS 3.1
- 8.9 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L - Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-40487- CVSS 3.1
- 8.9 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L - CVSS 3.1
- 9.0 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H - Weakness
- CWE-79, CWE-345, CWE-434
- Updated
- 2026-11-02
OSV
Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS
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.
- Record
CVE-2026-40487- CVSS 3.1
- 8.9 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L - Weakness
- CWE-345, CWE-434, CWE-79
- Updated
- 2026-11-02
Affected products
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| PoC in GitHub | Astaruf/CVE-2026-40487 | 2026-04-15 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD, OSV, PoC in GitHub |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-40487 is a high vulnerability (CVSS 8.9) in Gitroom Postiz, published April 18, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 13th percentile. No source names a fixed version.