Executive brief
Postiz, an AI-powered social media scheduling tool, contains a security flaw that allows attackers to bypass internal network protections. By exploiting a timing issue in how the software validates web addresses, an attacker can force the server to send requests to private internal services or cloud metadata endpoints. This could lead to the exposure of sensitive internal data, unauthorized interaction with private databases, or the theft of cloud security credentials.
Technical details
A Server-Side Request Forgery (SSRF) vulnerability exists in Postiz due to a Time-of-Check-Time-of-Use (TOCTOU) flaw in its URL validation logic. The function `isSafePublicHttpsUrl()` resolves a DNS name to validate that the target IP is public, but the subsequent `fetch()` call performs a second, independent DNS resolution. An attacker controlling a malicious DNS server can use DNS rebinding to return a safe IP during the check and an internal/private IP (such as 169.254.169.254 or localhost) during the actual request. This allows for internal network scanning, interaction with unauthenticated internal APIs, and potential access to cloud metadata services. The issue is patched in version 2.21.7.
Affected products
- Gitroom Postiz >= 2.16.6, < 2.21.7
Timeline
- 2026-04-16: disclosed: Report received by Postiz
- 2026-04-22: patched: Fix developed by Postiz
- 2026-04-27: advisory: Version 2.21.7 released
- 2026-05-08: other: CVE published to NVD