# CVE-2026-87927: MaxSite CMS local file inclusion via base64 path traversal

Source: https://junglewise.ai/threats/cve-2026-87927-maxsite-cms-local-file-inclusion-via-base64-path-traversal  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-09. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-87927 · Severity: high · CVSS 8.2 · Published 2026-09-09

MaxSite CMS is a website content management system that handles requests through dispatcher files. The vulnerability allows unauthenticated attackers to include and execute arbitrary PHP files by supplying specially crafted base64-encoded path traversal sequences, bypassing validation checks that are meant to restrict file access. This can lead to unauthorized code execution and exposure of sensitive administrative functionality.

## Quick answers

**Is CVE-2026-87927 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-87927 being exploited in the wild.

**How severe is CVE-2026-87927?** High severity, with a CVSS score of 8.2, published 9 September 2026.

**Which products and versions are affected?** MaxSite CMS through 109.6.

**Is there a fix for CVE-2026-87927?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-87927 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-87927?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

This is a local file inclusion (LFI) vulnerability in the ajax and require-maxsite dispatchers (application/views/ajax.php and application/views/require-maxsite.php). The root cause is a flawed path validation check: the code constructs a file path by concatenating base_dir with a base64-decoded attacker-controlled URI segment, then uses a substring check (strpos) to validate containment. Because the attacker input is appended to base_dir, the resulting path always contains base_dir as a leading substring even when the input contains ../ sequences that escape the intended directory. An unauthenticated attacker can send a request to /ajax/<base64-encoded-path> with a path traversal payload to include arbitrary files ending in -ajax.php or -require-maxsite.php. Included files are executed as PHP, potentially allowing code execution if a writable handler file is reached. The fix requires replacing the substring check with canonical path resolution (realpath) and explicitly rejecting .. sequences or maintaining an allowlist of permitted handlers.

## Affected products

- MaxSite CMS through 109.6

## Timeline

- 2026-09-09: disclosed

## References

- [https://github.com/EviL0rd/maxsite-cve1/blob/main/2026.09.08-maxsite-cms-ajax-lfi-path-traversal.md](https://github.com/EviL0rd/maxsite-cve1/blob/main/2026.09.08-maxsite-cms-ajax-lfi-path-traversal.md)
- [https://github.com/maxsite/cms](https://github.com/maxsite/cms)