CVE-2026-40487

HIGH
Published Apr 18, 2026 Modified Apr 23, 2026 CWE-79 CWE-345 CWE-434

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.

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CVSS v3.1 Score

8.9
HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L

EPSS — Exploit Prediction

0.0002
Probability of exploitation
0.06%
Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)
CWE-345 CWE-345
CWE-434 Unrestricted Upload

Affected Products

Vendor Product
gitroom postiz

References

Frequently Asked Questions

What is CVE-2026-40487? +
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. It has a CVSS v3.1 base score of 8.9 (HIGH).
How severe is CVE-2026-40487? +
CVE-2026-40487 has a CVSS v3.1 score of 8.9 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.
What products are affected by CVE-2026-40487? +
CVE-2026-40487 affects products from gitroom, specifically: postiz. Check the affected products table above for specific version ranges.
How do I check if I'm vulnerable to CVE-2026-40487? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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