CVE-2026-27891 is a high-severity (CVSS 7.2) Improper Input Validation vulnerability in facturascripts/facturascripts. No vendor fix is recorded yet; mitigation options are listed below.
Remote Code Execution (RCE) via Zip Slip in Plugin Upload Mechanism
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-27891.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-27891 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 386,684 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
facturascripts/facturascriptsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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.
Impact
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | facturascripts/facturascripts | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for facturascripts/facturascripts, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of facturascripts/facturascripts has shipped for CVE-2026-27891 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.
Frequently Asked Questions
Is CVE-2026-27891 in your dependencies?
Find it across Packagist, including transitive dependencies.