Postiz: TOCTOU DNS rebinding bypasses all SSRF URL validation paths

Description

Postiz is an AI social media scheduling tool. From version 2.16.6 to before version 2.21.7, all SSRF protections added in v2.21.4–v2.21.6 share a fundamental TOCTOU (Time-of-Check-Time-of-Use) vulnerability: isSafePublicHttpsUrl() resolves DNS to validate the target IP, but subsequent fetch() calls resolve DNS independently. An attacker controlling a DNS server can exploit this gap via DNS rebinding to redirect requests to internal network addresses. This issue has been patched in version 2.21.7.

Scores

EPSS (exploitation in 30 days)

0.22% · top 87% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.

Weakness

• CWE-918: Server-Side Request Forgery (SSRF) (opens in a new tab)All about CWE-918 and its CVEs

Affected products

• gitroomhq · postiz-app

  • affected >= 2.16.6, < 2.21.7

References (3)

• https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-f7jj-p389-4w45 (opens in a new tab)x_refsource_CONFIRM
• https://github.com/gitroomhq/postiz-app/commit/071143dcb01cdeb9d5d7019892f4c6ff7b19dbeb (opens in a new tab)x_refsource_MISC
• https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.7 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-42346](https://trackcve.app/badge/CVE-2026-42346.svg)](https://trackcve.app/cve/CVE-2026-42346)

Record last updated 11 May 2026, 14:35 UTC.