CVE-2026-18856 in Rhymix CMS
Summary
by MITRE • 08/05/2026
A vulnerability was determined in Poesis Rhymix CMS up to 2.1.33. This impacts the function procImporterAdminCheckXmlFile of the file modules/importer/importer.admin.controller.php of the component Data Import Module. This manipulation of the argument filename causes server-side request forgery. The attack is possible to be carried out remotely. The exploit has been publicly disclosed and may be utilized. Upgrading to version 2.1.34 will fix this issue. It is recommended to upgrade the affected component.
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Analysis
by VulDB Data Team • 08/05/2026
The vulnerability identified in Poesis Rhymix CMS version 2.1.33 and earlier represents a critical server-side request forgery weakness that stems from improper input validation within the data import module. This security flaw exists specifically within the procImporterAdminCheckXmlFile function located in modules/importer/importer.admin.controller.php, where the filename argument lacks adequate sanitization mechanisms. The vulnerability allows attackers to manipulate the filename parameter in ways that can trigger unauthorized server-side requests to arbitrary URLs, potentially enabling malicious actors to perform actions such as accessing internal network resources or conducting further reconnaissance attacks.
The technical nature of this vulnerability aligns with CWE-918, which classifies server-side request forgery attacks as a serious concern where applications fail to properly validate and sanitize user-provided input that influences HTTP requests. This flaw operates under the ATT&CK framework's technique T1105 for remote access and command execution, as it enables attackers to leverage the CMS's legitimate import functionality to make unauthorized requests to external systems. The vulnerability's remote exploitability means that attackers can trigger this issue without requiring physical access or local privileges, making it particularly dangerous in web-facing environments.
The operational impact of this vulnerability extends beyond simple data exfiltration or command execution, as it creates potential pathways for attackers to escalate their privileges within the affected system. When an attacker successfully exploits this flaw, they can potentially access internal services that would normally be protected by network segmentation, thereby undermining the security boundaries of the web application. The risk is amplified because the exploit has been publicly disclosed and may already be in use by threat actors, as indicated by the vulnerability report's statement about public exploitation. This makes the affected systems immediately vulnerable to active attacks rather than merely theoretical threats.
Organizations running Poesis Rhymix CMS versions prior to 2.1.34 face significant security risks that require immediate remediation. The recommended solution of upgrading to version 2.1.34 addresses the root cause by implementing proper input validation and sanitization for the filename parameter within the import module's administrative functions. Additionally, system administrators should consider implementing network-level restrictions to limit outbound connections from the CMS server, particularly to prevent unauthorized access to internal services. The mitigation strategy should also include monitoring for suspicious import activities and reviewing access logs for potential exploitation attempts, as these measures can provide early detection of compromise attempts that may not yet be fully automated or widely known in the threat landscape.