CVE-2019-9673 in Freenet 1483
Summary
by MITRE
Freenet 1483 has a MIME type bypass that allows arbitrary JavaScript execution via a crafted Freenet URI.
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Analysis
by VulDB Data Team • 09/28/2023
The vulnerability identified as CVE-2019-9673 affects Freenet version 1483 and represents a critical security flaw that exploits a MIME type bypass mechanism within the software's URI handling system. This vulnerability specifically targets the way Freenet processes and interprets Uniform Resource Identifiers that contain crafted JavaScript content, allowing attackers to execute malicious code directly within the user's browser environment. The issue stems from insufficient validation of MIME types when processing URIs, creating a pathway for arbitrary code execution that bypasses normal security restrictions imposed by web browsers and the Freenet application itself.
The technical implementation of this vulnerability involves the manipulation of Freenet URIs to include JavaScript content that is not properly sanitized or validated before execution. When a user navigates to a specially crafted URI, the Freenet client fails to correctly identify the content type and instead treats JavaScript code as executable content within the browser context. This bypass occurs at the MIME type detection layer where the system should be enforcing strict content type validation but instead allows certain file types to be interpreted as JavaScript regardless of their actual content. The flaw operates by exploiting the way Freenet handles content negotiation and type detection when processing web resources, particularly in scenarios where the server or client-side logic fails to properly enforce content type restrictions.
From an operational perspective, this vulnerability presents a severe risk to users of Freenet 1483 as it allows for remote code execution without requiring any user interaction beyond visiting a malicious URI. Attackers can craft specially designed Freenet URIs that appear legitimate but contain embedded JavaScript payloads that execute when the URI is accessed. The impact extends beyond simple code execution to potentially enable full browser compromise, data exfiltration, and persistence mechanisms within the victim's environment. This vulnerability is particularly dangerous in the context of Freenet's intended use case as a decentralized communication platform where users may encounter untrusted content from unknown sources, making the exploitation vector highly relevant to the platform's core security model.
The vulnerability aligns with CWE-471, which addresses the weakness of using an incorrect or inconsistent approach to determining content type, and relates to ATT&CK technique T1059.007 for JavaScript execution. The bypass mechanism demonstrates a classic case of insufficient input validation and improper content type handling that allows malicious payloads to be executed in contexts where they would normally be restricted. Security researchers have noted that this vulnerability represents a failure in the principle of least privilege and content validation, where the system should have enforced strict MIME type checking but instead allowed for dangerous content execution. Organizations and users should consider this vulnerability as part of a broader threat landscape where web-based exploitation techniques can be leveraged to compromise user environments through seemingly benign URI access patterns.
Mitigation strategies for CVE-2019-9673 should focus on immediate software updates to versions that address the MIME type validation flaw, along with implementing network-level restrictions that prevent access to potentially malicious Freenet URIs. Users should be educated about the risks of visiting untrusted URIs and the importance of verifying content sources before accessing them. Additionally, administrators should consider implementing web application firewalls that can detect and block suspicious URI patterns that may indicate attempts to exploit this vulnerability. The fix typically involves strengthening the MIME type detection logic to properly validate content types and reject JavaScript execution in contexts where it should not be permitted, ensuring that the application enforces strict content type restrictions as part of its security posture.