CVE-2026-90915 in Extension
Summary
by MITRE • 09/29/2026
Joomla! Core - [20260905] - Core - Arbitrary directory deletion via cache purge action in Joomla 4.0.0-5.4.8, 6.0.0-6.1.3 -An improper validation of the cache group name allowed path traverals in the file storage of the caching layer, resulting in arbitrary directory deletions.
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Analysis
by VulDB Data Team • 09/29/2026
The vulnerability identified as CVE-20260905 represents a critical security flaw within the Joomla! content management system affecting versions 4.0.0 through 5.4.8 and 6.0.0 through 6.1.3. This issue stems from an improper validation mechanism in the core caching layer, specifically during the cache purge operation. The root cause lies in the failure to adequately sanitize or validate the group name parameter provided by the user when initiating a cache clearing action. In web applications that utilize file-based storage for caching data, it is imperative that any directory names derived from user input are strictly validated against path traversal sequences such as dot-dot-slash (../). The absence of this validation allows an attacker to manipulate the intended target directory structure, effectively bypassing security boundaries designed to isolate cache files within specific application directories.
From a technical perspective, the flaw enables arbitrary directory deletion on the underlying server file system. When the Joomla process. This capability transforms what appears to be a routine maintenance function into a powerful vector for destructive actions against the server infrastructure.
The operational impact of this vulnerability is severe and potentially catastrophic for organizations relying on Joomla shares resources with other applications on the same server account, this vulnerability could potentially impact neighboring services, leading to broader system instability and data loss across multiple projects hosted under a single hosting environment.
This vulnerability aligns closely with CWE-22 Improper Limitation of a Pathname to a Restricted Directory, as it involves path traversal that allows access outside restricted boundaries. Additionally, the exploitation method corresponds to ATT&CK technique T1070 Indicator Removal on Host, specifically subtechnique T1070.004 File Deletion, which describes adversaries deleting files or folders to hinder forensic analysis and incident response efforts. The lack of input validation also reflects CWE-20 Improper Input Validation, highlighting a fundamental failure in the application's security design principles regarding trust boundaries for user-supplied data used in file system operations.
Mitigation strategies must prioritize immediate patching as the primary defense vector. Administrators should upgrade Joomla process runs with minimal privileges necessary for operation, thereby limiting the scope of directories that can be affected even if an exploitation attempt succeeds.