How to Fix CVE-2026-34577: postiz-app (Bundle Sibling)

*By Sai Kiran Pandrala*

Last verified: 2026-05-25

CVE-2026-34577 is a sibling vulnerability in the same Gitroomhq postiz-app advisory bundle as CVE-2026-34576. The same patched build closes every CVE in the bundle, so the remediation procedure for CVE-2026-34577 matches the primary write-up.

What is different about CVE-2026-34577?

Postiz is an AI social media scheduling tool. Prior to version 2.21.3, the GET /public/stream endpoint in PublicController accepts a user-supplied url query parameter and proxies the full HTTP response back to the caller. The only validation is url.endsWith('mp4'), which is trivially bypassable by appending .mp4 as a query parameter value or URL fragment.

Impact is consistent with the bundle: server-side request forgery against internal resources. The patched build closes every code path in the advisory in one update.

How to fix CVE-2026-34577

Apply the patched build per the primary write-up: How to Fix CVE-2026-34576.

For a quick check, confirm the running version of postiz-app:

# Confirm the installed version via your package manager
dpkg -l | grep -i postiz-app   # Debian/Ubuntu
rpm -qa | grep -i postiz-app   # RHEL/CentOS/Rocky

Frequently asked questions

Is CVE-2026-34577 being actively exploited?

Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.

How severe is CVE-2026-34577?

CVSS rates it 8.6 (High). Use that score to set your patch priority alongside the other items in your queue.

Do I have to take postiz-app offline to apply the patch?

It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.

What if my vulnerability scanner still flags CVE-2026-34577 after I patch?

Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.

References

• Official vendor advisory: https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-mv6h-v3jg-g539
• NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-34577
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• Primary write-up: How to Fix CVE-2026-34576

*Written by Sai Kiran Pandrala. Last verified 2026-05-25. Part of the Gitroomhq postiz-app advisory bundle. Full procedure at how-to-fix-cve-2026-34576.*