CWE-530

Variant Abstraction Level
Pillar — Highest-level weakness category
Class — Abstract, language-independent
Base — Specific enough to detect
Variant — Tied to specific technology
Compound — Requires multiple weaknesses Incomplete MITRE CWE Status
Stable — Fully reviewed and complete
Draft — Under development, may change
Incomplete — Partially defined by MITRE
Deprecated — No longer recommended
Obsolete — Replaced by another CWE
Exposure of Backup File to an Unauthorized Control Sphere

Description

A backup file is stored in a directory or archive that is made accessible to unauthorized actors.

Often, older backup files are renamed with an extension such as .~bk to distinguish them from production files. The source code for old files that have been renamed in this manner and left in the webroot can often be retrieved. This renaming may have been performed automatically by the web server, or manually by the administrator.

Consequences

Confidentiality — Read Application Data

At a minimum, an attacker who retrieves this file would have all the information contained in it, whether that be database calls, the format of parameters accepted by the application, or simply information regarding the architectural structure of your site.

Mitigations

Phase: Policy

Recommendations include implementing a security policy within your organization that prohibits backing up web application source code in the webroot.

Detection

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)