CVE-2026-42556: Postiz is an AI social media scheduling tool

Routine

HIGH 8.9DOWNGRADE

CVE-2026-42556 is a high-severity flaw (CVSS 8.9) affecting postiz. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Postiz is an AI social media scheduling tool. From version 2.21.6 to before version 2.21.7, any authenticated user who can create a post can store arbitrary HTML in post content by tampering their own save request and send the public preview link /p/<postId>?share=true to another user. The preview page renders that stored HTML with dangerouslySetInnerHTML on the main application origin. This issue has been patched in version 2.21.7.

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.9 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.3% (top 83%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-05-08
Last modified	2026-07-24

Publisher (CNA): GitHub, Inc. · Vendor: gitroom

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-08 23:16 UTCPublished CVE record published
2026-07-24 21:10 UTCUpdated Record last modified

gitroom postiz DOWNGRADE

Affected: 2.21.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.21.6

1. Check installed version

apt-cache policy postiz || rpm -q postiz || postiz --version

2. No fixed release: DOWNGRADE to a release before 2.21.6 (Debian / Ubuntu)

apt-cache madison postiz sudo apt install postiz=<VERSION_BEFORE_2.21.6> sudo apt-mark hold postiz

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list postiz sudo dnf downgrade postiz-<VERSION_BEFORE_2.21.6> sudo dnf versionlock add postiz

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42556?

postiz: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-42556 being exploited?

CVE-2026-42556 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42556 affect?

CVE-2026-42556 affects postiz. Severity is high (CVSS 8.9). Postiz is an AI social media scheduling tool. From version 2.21.6 to before version 2.21.7, any authenticated user who can create a post can store arbitrary HTML in post content by tampering their own save request and send the public previe

How urgent is CVE-2026-42556?

Priority 35/100. High severity

Related CVEs

CVE-2026-40168 HIGH 8.2 UPGRADE Postiz is an AI social media scheduling tool
CVE-2026-40487 HIGH 8.9 UPGRADE Postiz is an AI social media scheduling tool
CVE-2026-42298 CRITICAL 10.0 UPGRADE Postiz is an AI social media scheduling tool

References

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