CVE-2026-104476 in Backdrop
Summary
by MITRE • 10/03/2026
Backdrop CMS before 1.35.1 contains an information disclosure vulnerability that allows unauthenticated attackers to retrieve configuration export archives left on the server after transfer. Attackers can download compressed archives generated by users with configuration export permission to obtain the full site configuration, including sensitive settings.
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Analysis
by VulDB Data Team • 10/03/2026
Backdrop CMS versions prior to 1.35.1 are susceptible to an information disclosure vulnerability that stems from improper handling of temporary files during the configuration management workflow. The core technical flaw lies in the persistence of compressed archive files on the server filesystem after they have been generated for transfer purposes but not subsequently cleaned up or properly secured against unauthorized access. When a user with specific permissions initiates a configuration export, the system creates a tarball containing the complete site configuration data and stores it temporarily within the web-accessible directory structure. However, due to insufficient cleanup mechanisms or incorrect file permission settings, these archive files remain accessible via direct URL requests even after the intended transfer process is completed or abandoned by the user. This oversight allows unauthenticated attackers to enumerate and download these archives without needing valid credentials for the CMS administrative interface.
The operational impact of this vulnerability is significant because configuration export archives in Backdrop CMS contain a comprehensive dump of the site's settings, including database connection strings, API keys, secret salts, and other sensitive environmental variables. By extracting and analyzing these files, an attacker can gain deep insight into the application's architecture and security posture. This information serves as critical reconnaissance data that facilitates further attacks such as credential stuffing, session hijacking, or privilege escalation if combined with other vulnerabilities. The ability to retrieve full site configuration effectively compromises the confidentiality of the entire web application environment, potentially leading to complete system compromise depending on how securely those secrets are managed elsewhere in the infrastructure.
From a classification perspective, this vulnerability aligns closely with CWE-209 which describes the generation of an error message that includes sensitive information about the software, the operating system, the database, or other internal implementation details when attempting to access resources without proper authorization. It also relates to CWE-538 regarding file and directory information exposure where files are left in a location accessible by unauthorized users. In terms of attack vectors, this scenario maps to ATT&CK technique T1005 which covers Data from Local System Retrieval, specifically through the mechanism of local file access or scraping unsecured temporary storage locations. The lack of authentication requirement places it firmly within the realm of remote information gathering that does not require initial foothold on the system.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Administrators should immediately upgrade to Backdrop CMS version 1.35.1 or later where this issue has been addressed by ensuring temporary configuration files are securely deleted after use or stored in non-web-accessible directories with restrictive permissions. Additionally, implementing strict file permission controls on the web root can prevent direct access to sensitive artifacts even if they persist temporarily. Security teams should also audit their deployment pipelines to ensure that any automated processes generating large data exports include explicit cleanup steps and verify that no residual files remain exposed after task completion. Regular vulnerability scanning and configuration audits are recommended to detect similar patterns in other content management systems or custom applications where temporary file handling may be similarly flawed.