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CVE-2026-87927 – Unauthenticated Local File Inclusion – MaxSite CMS 0.78 through 109.6

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Summary

CVE-2026-87927 is a local file inclusion (LFI) vulnerability in MaxSite CMS’s ajax and require-maxsite request dispatchers, affecting versions 0.78 through 109.6. Insufficient path validation allows unauthenticated remote attackers to include and execute privileged handler files that would normally be reachable only by authenticated/admin users. The issue carries a CVSS v3.1 base score of 8.2 (High), with the CVE record itself flagging network-exploitable, no-privilege, no-interaction access as high severity (8.8 under CVSS v4.0).

Technical details

  • Root cause: application/views/ajax.php and application/views/require-maxsite.php build a file path by concatenating the configured base directory with a base64-decoded value taken from the request URI, then validate containment using a naive substring check (strpos($fn1, $base_dir) === false) rather than canonical path resolution.
  • Because the concatenated path always contains the base directory as a leading substring, ../ traversal sequences embedded in the base64-decoded segment can escape the intended subdirectory while still passing the check.
  • Trigger conditions: an unauthenticated request to an /ajax/ (or require-maxsite) endpoint containing a base64-encoded traversal path, where the target file ends in -ajax.php or -require-maxsite.php; requests are typically sent with an X-Requested-With: XMLHttpRequest header.
  • Attack vector: network, no authentication or user interaction required, low attack complexity.
  • Impact: the resulting require() call executes arbitrary handler files within the installation, allowing attackers to invoke admin-gated handler logic without credentials — CVSS impact is rated low confidentiality / high integrity, no availability impact.

Affected software

  • MaxSite CMS versions 0.78 through 109.6 (inclusive)

Severity

  • CVSS v3.1 Base Score: 8.2 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

Mitigation and recommended actions

  • Immediate: No vendor-confirmed patched release has been publicly documented as of this writing. Monitor the MaxSite CMS project for an update beyond 109.6 and apply it as soon as it is available.
  • If no patch: Restrict or firewall access to /ajax/* and require-maxsite endpoints from untrusted networks; deploy WAF/reverse-proxy rules to block requests containing base64-decodable path traversal sequences (e.g., decoded values containing ../) in these paths; monitor logs for anomalous requests to ajax/require-maxsite dispatchers with unexpected file suffixes.

How IONIX identifies potentially affected assets

IONIX matches the following signal against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Generator meta tag content: MaxSite CMS

References

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