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

> Attackers can bypass SSRF protections via DNS rebinding to access internal network resources in Postiz.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 May 2026
- **Updated:** 11 May 2026
- **Also known as:** GHSA-f7jj-p389-4w45

## What is CVE-2026-42346?

CVE-2026-42346 is a medium-severity server-side request forgery vulnerability in gitroomhq postiz-app, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-42346?


## How do I fix CVE-2026-42346?

No fix has been published for CVE-2026-42346 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-42346 being exploited?

There is no known exploitation of CVE-2026-42346 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42346 and fix it if it is affected.

What it is: CVE-2026-42346 is a medium-severity server-side request forgery vulnerability in gitroomhq postiz-app, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42346 in the wild and no public exploit code.

Affected product: gitroomhq postiz-app. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42346/ (Markdown: https://insights.sbomify.com/CVE-2026-42346/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42346
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42346
- OSV: https://osv.dev/vulnerability/CVE-2026-42346

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42346/
Summaries are generated and may contain mistakes; the official description above is the record.