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CVE-2026-42556: Gitroom Postiz Cross Site Scripting (CVSS 8.9)

CVE-2026-42556 is a high severity cross site scripting in Gitroom Postiz with a CVSS score of 8.9. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Last updated: Jul 24, 2026

Quick answer

Direct answer

CVE-2026-42556 is a high severity cross site scripting in Gitroom Postiz with a CVSS score of 8.9. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Risk scores

CVSS base score
8.9HIGH
EPSS probability
0.44%
Higher than 36 percent of all CVEs
CISA KEV
Not listed
CVSS metricWhat it means
Attack vector (AV:N)Network: reachable remotely
Attack complexity (AC:L)Low complexity
Privileges required (PR:L)Low privileges required
User interaction (UI:R)A user must take an action
Scope (S:C)Scope changed: impact spreads beyond the component
Confidentiality (C:H)High confidentiality impact
Integrity (I:H)High integrity impact
Availability (A:L)Low availability impact

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L

About Gitroom Postiz

CVE-2026-42556 affects Gitroom Postiz, a product from Gitroom. Before acting, confirm where Gitroom Postiz runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.

What the flaw is

In plain terms: 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.

The weakness class is Cross Site Scripting. Attacker supplied script runs in another user's browser inside the trusted site.

Based on its CVSS vector, the flaw can be reached over the network, needs some level of access, and relies on a user taking an action. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Affected versions and timeline

FieldDetail
ProductGitroom Postiz
Affected versionsPostiz 2.21.6
PublishedMay 8, 2026
Last modifiedJul 24, 2026
Added to CISA KEVNot listed
Assigning CNAsecurity-advisories@github.com

How to detect it

  • Inventory every instance of Gitroom Postiz and record the running version against the affected range above.
  • Check external attack surface scans for internet facing instances of the component.
  • Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
  • Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.

How to fix it

  • Apply the fixed version of Gitroom Postiz named in the vendor advisory.
  • If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
  • Rescan after the change to prove the exposure is gone, then close the ticket.

CTEM action plan

CTEM stageWhat to do for this CVE
ScopeAdd every business service that depends on Gitroom Postiz to the current CTEM cycle.
DiscoverFind all instances, including shadow and cloud deployments, and record versions and exposure.
PrioritizeRank using EPSS and CVSS together with asset exposure and business impact.
ValidateConfirm the flaw is reachable and exploitable in your environment and that compensating controls work.
MobilizeAssign the fix to the asset owner with a due date matched to the priority, then verify closure.

CWE References

Technical References

Frequently asked questions

CVE-2026-42556 is a high severity cross site scripting in Gitroom Postiz with a CVSS score of 8.9. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

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