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CVE-2026-75873 – Unauthenticated Arbitrary File Upload / RCE – Zella Theme WordPress Theme < 2.6.3

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Summary

CVE-2026-75873 is a critical unrestricted file upload vulnerability in the Zella WordPress theme affecting all versions prior to 2.6.3. One of the theme’s font upload actions performs no capability or nonce check and is reachable by unauthenticated users, allowing attackers to upload arbitrary files—including PHP files—and achieve remote code execution. The flaw has a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: A font upload action (AJAX handler) in the Zella theme fails to perform any capability check or nonce/CSRF verification before processing uploaded files.
  • Trigger conditions: The vulnerable action is registered and accessible to unauthenticated (unauthorized) users, requiring no login or prior access to the WordPress site.
  • Attack vector: Network — an attacker sends a crafted request to the exposed font upload endpoint and uploads a file with an arbitrary extension, including .php.
  • Impact: Successful exploitation allows arbitrary file upload, enabling attackers to place a web shell and achieve full remote code execution on the underlying server, compromising confidentiality, integrity, and availability of the site and potentially the host.

Affected software

  • Zella WordPress theme: all versions prior to 2.6.3

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Update the Zella theme to version 2.6.3 or later, which adds the missing capability/nonce checks to the font upload action.
  • If immediate patching is not possible:
    • Restrict or disable access to the vulnerable font upload AJAX action at the web server or WAF layer until the update can be applied.
    • Monitor for unexpected PHP or executable files appearing in uploads directories.
    • Review server logs for unauthenticated requests to theme-related AJAX endpoints associated with font uploads.
    • Consider taking the site offline or placing it behind authenticated access until patched, given the unauthenticated, network-exploitable nature of this issue.

References

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