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.

CVSS v3 8.9 HIGH

8.9^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.3 / Impact : 6.0

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction REQUIRED

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact LOW

Scope CHANGED

References

Link	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

Configurations

Configuration 1 (hide)

cpe:2.3:a:gitroom:postiz:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-04-18 02:16

Updated : 2026-06-17 10:45

NVD link : CVE-2026-40487

Mitre link : CVE-2026-40487

CVE.ORG link : CVE-2026-40487

JSON object : View

Products Affected

gitroom

postiz

CWE

CWE-79

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CWE-345

Insufficient Verification of Data Authenticity

CWE-434

Unrestricted Upload of File with Dangerous Type

{"id": "CVE-2026-40487", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-40487", "role": "CISA Coordinator", "options": [{"exploitation": "poc"}, {"automatable": "no"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-04-20T15:25:37.579242Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "security-advisories@github.com", "cvssData": {"scope": "CHANGED", "version": "3.1", "baseScore": 8.9, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L", "integrityImpact": "HIGH", "userInteraction": "REQUIRED", "attackComplexity": "LOW", "availabilityImpact": "LOW", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}, "impactScore": 6.0, "exploitabilityScore": 2.3}, {"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "CHANGED", "version": "3.1", "baseScore": 9.0, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "REQUIRED", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}, "impactScore": 6.0, "exploitabilityScore": 2.3}]}, "affected": [{"source": "security-advisories@github.com", "affectedData": [{"vendor": "gitroomhq", "product": "postiz-app", "versions": [{"status": "affected", "version": "< 2.21.6"}]}]}], "published": "2026-04-18T02:16:11.670", "references": [{"url": "https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6", "tags": ["Product", "Release Notes"], "source": "security-advisories@github.com"}, {"url": "https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx", "tags": ["Exploit", "Vendor Advisory"], "source": "security-advisories@github.com"}, {"url": "https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx", "tags": ["Exploit", "Vendor Advisory"], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "security-advisories@github.com", "description": [{"lang": "en", "value": "CWE-79"}, {"lang": "en", "value": "CWE-345"}, {"lang": "en", "value": "CWE-434"}]}], "descriptions": [{"lang": "en", "value": "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."}], "lastModified": "2026-06-17T10:45:22.020", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:gitroom:postiz:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "E5AA1AE0-803D-40DD-9D8B-4B166691D8B9", "versionEndExcluding": "2.21.6"}], "operator": "OR"}]}], "sourceIdentifier": "security-advisories@github.com"}