CVE-2026-74253 in Sourcerer Extension
Summary
by MITRE • 08/17/2026
Joomla Extension - regularlabs.com - Unauthenticated RCE through unverified reflected user input in Sourcerer < 14.0.0 - Regular Labs Sourcerer before 14.0.0 processes {source} blocks found in Joomla’s final rendered HTML without reliably determining where that code originated.
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Analysis
by VulDB Data Team • 08/17/2026
The vulnerability identified involves a critical Remote Code Execution flaw within the Regular Labs Sourcerer extension for Joomla, specifically affecting versions prior to 14.0.0. This security issue stems from an unverified reflection of user-controlled input during the processing of dynamic content blocks. The core mechanism relies on how the extension parses and executes PHP code embedded within {source} tags that appear in the final rendered HTML output of a Joomla page. Instead of strictly validating whether these code snippets originated from trusted, server-side sources such as database entries or administrator-configured modules, the application processes them based solely on their presence in the client-visible markup. This architectural oversight allows attackers to inject malicious PHP payloads directly into web pages through unauthenticated means, bypassing traditional authentication barriers that typically protect administrative functions and sensitive data processing logic.
From a technical perspective, this flaw represents a severe instance of Server-Side Request Forgery combined with Arbitrary Code Execution principles. When a user requests a page containing the vulnerability, or when an attacker manipulates input parameters that get reflected into the HTML structure, the Sourcerer extension intercepts these {source} blocks during the rendering phase. Because the validation logic fails to distinguish between legitimate content authored by administrators and maliciously injected code from external sources, it proceeds to evaluate and execute the embedded PHP commands on the server side. This behavior effectively turns any publicly accessible page that renders user-modifiable or reflected input into a potential command execution vector. The lack of strict origin verification means that even if an attacker cannot directly upload files to the server, they can still achieve full system compromise by tricking the application into executing arbitrary code embedded within HTTP requests or manipulated HTML structures.
The operational impact of this vulnerability is profound and immediate. An unauthenticated remote attacker can exploit this flaw to execute arbitrary PHP commands with the privileges of the web server process. This typically results in complete control over the underlying Joomla installation, including access to sensitive database information, modification of site configurations, defacement of public-facing content, and potentially pivoting into internal network infrastructure if the server is part of a larger environment. The ability to execute code without authentication significantly lowers the barrier for exploitation, allowing automated scanning tools and opportunistic attackers to compromise vulnerable sites with minimal effort. This aligns closely with CWE-94 Improper Control of Generation of Code or Script, as well as CWE-78 OS Command Injection if the executed PHP commands interact directly with system-level utilities. Furthermore, in terms of offensive security frameworks like MITRE ATT&CK, this vulnerability facilitates techniques related to Remote Services and Application Layer Protocol exploitation, enabling initial access and subsequent privilege escalation within the web application context.
To mitigate this risk, administrators must immediately upgrade Regular Labs Sourcerer to version 14.0.0 or later, where these validation checks have been strengthened to ensure that only explicitly authorized sources are processed for dynamic code execution. Until an update is applied, it is advisable to disable the extension entirely if its advanced features are not strictly required, thereby removing the attack surface associated with {source} block processing. Additionally, implementing a Web Application Firewall can provide a layer of defense by detecting and blocking patterns indicative of PHP injection attempts within HTTP requests. Organizations should also conduct thorough audits of their Joomla installations to identify any remaining instances of unpatched extensions and ensure that all third-party components are kept up to date with the latest security patches provided by their respective vendors. Regular monitoring for unusual server activity or unexpected outbound connections can help detect potential exploitation attempts in real-time, although proactive patching remains the most effective remediation strategy.