CVE-2017-17516 in Reddit Terminal Viewer
Summary
by MITRE
scripts/inspect_webbrowser.py in Reddit Terminal Viewer (RTV) 1.19.0 does not validate strings before launching the program specified by the BROWSER environment variable, which might allow remote attackers to conduct argument-injection attacks via a crafted URL.
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Analysis
by VulDB Data Team • 12/15/2019
The vulnerability identified as CVE-2017-17516 resides within the Reddit Terminal Viewer (RTV) version 1.19.0, specifically in the scripts/inspect_webbrowser.py file. This flaw represents a critical security oversight that enables remote attackers to execute argument injection attacks through manipulated URL inputs. The vulnerability stems from insufficient input validation mechanisms that fail to sanitize or verify strings before these inputs are used to launch external programs via the BROWSER environment variable.
The technical nature of this vulnerability aligns with CWE-77 and CWE-94, categorizing it as a command injection flaw where untrusted data flows directly into system execution contexts. When RTV processes URLs through the inspect_webbrowser.py script, it does not properly validate or escape the strings before incorporating them into the command line arguments that are passed to the system's web browser launcher. This creates an environment where malicious actors can craft URLs containing specially formatted strings that, when processed by the vulnerable script, result in arbitrary command execution on the target system.
The operational impact of this vulnerability extends beyond simple privilege escalation as it allows attackers to execute arbitrary commands with the privileges of the user running RTV. An attacker could potentially leverage this flaw to execute malicious payloads, establish persistent access, or conduct further reconnaissance within the compromised system. The remote nature of the attack means that adversaries do not require physical access or local credentials to exploit this vulnerability, making it particularly dangerous in multi-user environments or when RTV is used in automated or shared computing scenarios.
The ATT&CK framework categorizes this vulnerability under T1059.001 (Command and Scripting Interpreter: PowerShell) and T1203 (Exploitation for Client Execution) as it enables adversaries to execute commands through legitimate system interfaces. The vulnerability's exploitation requires minimal prerequisites, as it only necessitates the ability to influence the URL content that RTV processes, which can be achieved through various attack vectors including phishing, malicious website redirection, or compromised content delivery systems.
Mitigation strategies should focus on implementing proper input validation and sanitization mechanisms within the RTV application. The most effective approach involves parameterizing the BROWSER environment variable usage and employing secure coding practices that prevent direct string concatenation into system execution contexts. Additionally, developers should implement proper string escaping or encoding when dealing with external program invocations. The vulnerability can be addressed through input validation that filters or rejects potentially malicious strings, and by implementing proper command line argument handling that ensures only expected and safe parameters are passed to system executables. Users should also consider updating to patched versions of RTV, as this vulnerability was resolved in subsequent releases through proper input validation implementations.