CVE-2018-5182 in Firefox
Summary
by MITRE
If a text string that happens to be a filename in the operating system's native format is dragged and dropped onto the addressbar the specified local file will be opened. This is contrary to policy and is what would happen if the string were the equivalent "file:" URL. This vulnerability affects Firefox < 60.
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Analysis
by VulDB Data Team • 07/20/2024
This vulnerability represents a critical security flaw in Mozilla Firefox browsers prior to version 60, where the application fails to properly validate user input during drag and drop operations involving file paths. The issue arises when a user drags and drops a text string that happens to correspond to a local file path in the operating system's native format directly onto the browser's address bar. The browser incorrectly interprets this action as a request to open the specified local file, effectively bypassing normal security boundaries that should prevent such direct file access through web interface interactions. This behavior fundamentally violates the principle of least privilege and creates an unexpected attack vector that could be exploited by malicious actors to gain unauthorized access to local system resources.
The technical implementation of this vulnerability stems from Firefox's insufficient sanitization and validation of input received through drag and drop operations in the address bar component. When a user performs a drag and drop action onto the address bar, the browser should treat the input as a URL or web resource request rather than attempting to interpret it as a local file path. However, the application's logic fails to properly distinguish between legitimate web URLs and potentially dangerous local file references, particularly when the input string matches the native file system path format of the underlying operating system. This flaw operates at the intersection of web browser interface handling and operating system file path interpretation, creating a dangerous overlap that allows for arbitrary file access through seemingly benign user interactions.
The operational impact of this vulnerability extends beyond simple file access, as it provides potential attackers with a method to execute arbitrary local file operations without proper authorization. An attacker could craft malicious text strings that, when dropped onto the address bar, would cause the browser to open sensitive local files, execute local programs, or potentially trigger other system-level operations depending on the target operating system. The vulnerability is particularly concerning because it requires no special privileges beyond normal browser usage and can be triggered through social engineering tactics where users are convinced to drag and drop malicious content. This makes it highly exploitable in phishing campaigns or targeted attacks where an attacker can manipulate a user into performing the specific drag and drop action that triggers the vulnerability. The flaw essentially allows for a form of privilege escalation from web browsing context to local system access, violating fundamental security boundaries that should protect users from such cross-context operations.
The vulnerability aligns with several cybersecurity frameworks and threat models, including CWE-20, which describes improper input validation, and represents a classic example of a command injection vulnerability where user-supplied input is not properly sanitized before being processed. From an ATT&CK perspective, this flaw maps to techniques involving privilege escalation and initial access through social engineering, as it requires user interaction to be effective. Organizations affected by this vulnerability should immediately implement patch management procedures to upgrade to Firefox version 60 or later, where the issue has been resolved through improved input validation and sanitization of drag and drop operations in the address bar component. Additional mitigations include user education about the risks of drag and drop operations with unknown content, browser security policy enforcement, and monitoring for unusual address bar interactions that might indicate exploitation attempts. The fix implemented by Mozilla involved strengthening the validation logic to properly identify and reject local file path references when processing drag and drop operations in the address bar, ensuring that such inputs are treated as web resources rather than local system commands.