CVE-2026-42346: Postiz SSRF via DNS Rebinding TOCTOU in URL Validation

CVE-2026-42346 · Severity: medium · CVSS 6.5 · Published 2026-05-08

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.

Technologies: Gitroom Postiz. Vendors: Gitroom.

Quick answers

Is CVE-2026-42346 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-42346 being exploited in the wild.
How severe is CVE-2026-42346?
Medium severity, with a CVSS score of 6.5, published 8 May 2026.
Which products and versions are affected?
Gitroom Postiz >= 2.16.6, < 2.21.7.
Is there a fix for CVE-2026-42346?
A patch was published on 2026-04-22: Fix developed by Postiz Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-42346 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-42346?
Check whether you run Gitroom Postiz at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

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

References

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