External risk intelligence

Verot Class Upload PHAR File Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2019-19576

This vulnerability exists in a PHP file upload library commonly integrated into web applications and content management systems like Joomla! for processing user-submitted files. Because these libraries are typically embedded in internet-facing web applications to handle user uploads, the vulnerable code is commonly exposed to the public internet.

Unrestricted File Upload

Verot Project Verot

before 1.0.32.0.0 to before 2.0.42.10.1 and earlier

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns a critical vulnerability in a widely used PHP file upload library that could allow attackers to execute malicious code remotely. The issue stems from an oversight in how the library handles dangerous file extensions. If exploited, this could lead to a complete compromise of affected systems.

Vulnerability allows remote code execution.
Impacts systems processing user file uploads.
Confirm relevance and exposure to affected systems.

Attack Path

How an attacker could exploit the issue

An attacker can target a web application that uses a vulnerable file upload component. By uploading a specially crafted file, the attacker can bypass security checks and potentially execute arbitrary code on the server. This could lead to a complete compromise of the affected system.

No special access required.
Uploading a malicious file.
Remote code execution risk.

Live Threat

Current exploitation, exposure, and threat context

When supported by the advisory, this vulnerability could allow an attacker to upload and execute arbitrary code by bypassing file extension restrictions. This could affect the integrity and availability of web applications that use the affected library for file uploads.

Arbitrary code execution.
Remote file upload bypass.
System compromise.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability impacts web applications utilizing the verot.net class.upload.php library or Joomla! extensions like K2 that incorporate it. The first practical step involves identifying all instances of this library or affected extensions, determining their business criticality and internet exposure, and then confirming the responsible application or platform team to initiate a risk-based remediation plan.

Identify affected applications and owners.
Verify exposure and business impact.
Plan targeted remediation or vendor engagement.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the verot class.upload.php library used for?

This PHP library is a common developer tool used to handle file uploads in web applications. It simplifies tasks like checking file types, resizing images, and managing security. Because it is often integrated into content management systems like Joomla!—specifically within the K2 extension—it is frequently found in web platforms that allow users to submit files, such as profile pictures, attachments, or document uploads.

What does CWE-434 mean for CVE-2019-19576?

CWE-434 refers to an Unrestricted Upload of File with Dangerous Type. In this specific vulnerability, the library fails to recognize the .phar extension as a potential threat. Because the library does not block these files, an attacker can upload a malicious script disguised as a different file type. When the server processes this file incorrectly, it may execute the attacker's code, leading to a loss of control over the system.

How does an attacker trigger this vulnerability?

An attacker triggers this by uploading a file with a .phar extension to a web form managed by the vulnerable library. The library checks extensions to ensure safety, but because it misses the .phar extension, it accepts the malicious file. Simply having the library installed is not enough; the vulnerability is only triggered when the application accepts user-provided files that are then processed in a way that allows the malicious .phar code to execute on the server.

How do I know if this CVE affects my environment?

Halo Surface Signal indicates this vulnerability is common in internet-facing web applications. You are at higher risk if you run Joomla! with the K2 extension or any custom PHP application using the verot.net class.upload library. If these web applications are accessible to the public internet, they are prime candidates for this vulnerability, as the file upload features are exposed by design to handle legitimate user submissions.

What is the first step to remediate this issue?

Begin by auditing your web environment to create an inventory of where the verot.net library or K2 extension is active. Prioritize applications that allow file uploads and are accessible to the public. Once you have identified these instances, consult your development or platform teams to determine if you are using an affected version. If you are, plan to update the library to the secure versions (1.0.3, 2.0.4, or later) to effectively block .phar files and neutralize the risk.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.