CVE-2004-0473 in Web Browser
Summary
by MITRE
Argument injection vulnerability in Opera before 7.50 does not properly filter "-" characters that begin a hostname in a telnet URI, which allows remote attackers to insert options to the resulting command line and overwrite arbitrary files via (1) the "-f" option on Windows XP or (2) the "-n" option on Linux.
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Analysis
by VulDB Data Team • 07/12/2025
This vulnerability exists in Opera web browser versions prior to 7.50 and represents a classic argument injection flaw that exploits improper input validation in URI parsing. The vulnerability specifically targets the handling of telnet URIs where hostname parameters beginning with hyphen characters are not properly sanitized, allowing malicious actors to inject command line arguments that get passed to underlying system commands. The flaw occurs when Opera processes telnet URIs such as telnet://user-ffilename or telnet://user-nhostname, where the leading hyphen signals the beginning of a command line option that should be treated as part of the URI rather than as a system command parameter. This issue falls under CWE-77 which classifies improper neutralization of special elements used in command execution contexts, and specifically relates to command injection vulnerabilities that occur when user-supplied data is directly incorporated into system commands without proper sanitization. The vulnerability demonstrates a critical failure in input validation and sanitization of URI components that should be treated as opaque data rather than executable parameters.
The operational impact of this vulnerability is particularly severe as it enables remote code execution through carefully crafted telnet URIs that can be delivered via web pages, email links, or other attack vectors. On Windows XP systems, attackers can leverage the "-f" option to specify a filename for the telnet client to read, potentially allowing them to overwrite arbitrary files on the system or execute malicious code through file manipulation. On Linux systems, the "-n" option can be exploited to specify a hostname, which may result in similar file overwrite or command execution capabilities depending on the system configuration and telnet client implementation. The attack requires minimal user interaction beyond visiting a malicious webpage or clicking on a crafted link, making it particularly dangerous in phishing scenarios or when users browse untrusted websites. This vulnerability aligns with ATT&CK technique T1059.007 which covers command and scripting interpreter for execution, specifically targeting the use of system commands through web-based interfaces.
The root cause of this vulnerability stems from Opera's insufficient filtering of special characters in URI hostname components, particularly hyphens that are commonly used as command line option prefixes in Unix-like systems and Windows applications. When the browser processes these telnet URIs, it fails to properly escape or validate the hostname portion before passing it to the underlying telnet client, resulting in a situation where user-controlled input becomes part of the command line arguments. This represents a failure in the principle of least privilege and proper input sanitization, as the browser should treat all URI components as potentially malicious data that requires validation before system interaction. The vulnerability demonstrates how web browsers can become attack vectors for system-level exploits when they fail to properly validate and sanitize data that gets passed to operating system commands, creating a pathway for attackers to bypass traditional web application security controls. Organizations should implement immediate mitigations including browser updates to version 7.50 or later, network-based filtering of telnet URI schemes, and user education regarding the dangers of clicking on untrusted links that may contain malicious URIs.