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TI-2026-29238 Aliases CVE-2026-40487

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

Priority HIGH 74CWE-345Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
Required
Attack complexity
Low
Impact type
Security bypass, Code execution, Cross-site scripting
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-345, CWE-434 and CWE-79.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00224 13th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed postiz-app (gitroomhq): 2.21.6

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
gitroomhqpostiz-appbefore 2.21.62.21.6Patch availableCNA
  • postiz-app Vendorgitroomhq Affected before 2.21.6 Fixed in 2.21.6 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:gitroom:postiz:*:*:*:*:*:*:*:*before 2.21.6Vulnerablegitroomhq
  • cpe:2.3:a:gitroom:postiz:*:*:*:*:*:*:*:* Versions before 2.21.6 Vulnerable ·gitroomhq

Remediation

  • Fix · CNA postiz-app (gitroomhq) Fixed in 2.21.6

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-40487

References

Exploit 1

Other 1

  • TI-2026-26825 Postiz: Unauthenticated Full-Read SSRF via /public/stream Endpoint with Trivially Bypassable Extension Check CVSS 3.1HIGH 8.6
  • TI-2026-28982 Postiz has Server-Side Request Forgery via Redirect Bypass in /api/public/stream CVSS 3.1HIGH 8.2
  • TI-2026-26824 Postiz: SSRF in upload-from-url endpoint allows fetching internal resources and cloud metadata CVSS 4.0HIGH 8.3
  • TI-2026-26837 Postiz: SSRF via Webhook Creation Endpoint Missing URL Safety Validation CVSS 3.1MEDIUM 5.4
  • TI-2026-30607 Postiz: Arbitrary Code Execution and Token Exfiltration in pr-docker-build.yml via untrusted Dockerfile.dev CVSS 3.1CRITICAL 10.0
  • TI-2026-30836 Postiz stored XSS in public preview page CVSS 3.1CRITICAL 9.0

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences