CVE-2005-3901 in Flash Communication Server
Summary
by MITRE
Macromedia Flash Communication Server MX 1.0 and 1.5 does not sufficiently validate certain RTMP data, which allows attackers to cause a denial of service (instability or crash), as demonstrated using an alpha release build of Flash Player 8.5 (build 133).
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Analysis
by VulDB Data Team • 06/16/2019
The vulnerability described in CVE-2005-3901 represents a critical flaw in Macromedia Flash Communication Server MX versions 1.0 and 1.5 that stems from inadequate validation of Real-Time Messaging Protocol (RTMP) data. This issue manifests as a denial of service condition that can destabilize the server through carefully crafted malicious inputs. The vulnerability specifically targets the server's handling of RTMP protocol messages, which are fundamental to Flash's real-time communication capabilities. When the server receives malformed or unexpected RTMP data, it fails to properly validate the incoming information before processing it, leading to potential system instability or complete crash. The demonstration of this vulnerability using an alpha release build of Flash Player 8.5 reveals that even pre-release software can exploit this weakness, highlighting the broader implications for the entire Flash ecosystem. This type of vulnerability falls under the category of insufficient input validation, which is classified as CWE-20 by the Common Weakness Enumeration standard, representing one of the most prevalent classes of software vulnerabilities.
The technical exploitation of this vulnerability occurs through the manipulation of RTMP protocol messages that the Flash Communication Server processes. RTMP is a protocol designed for low-latency communication between Flash applications and servers, enabling features such as live streaming, chat applications, and collaborative tools. When the server receives RTMP data that does not conform to expected formats or contains unexpected values, the insufficient validation logic fails to properly sanitize or reject these inputs. This allows attackers to craft specially formatted RTMP messages that trigger buffer overflows, memory corruption, or other internal state inconsistencies within the server software. The vulnerability's impact is particularly severe because it can cause complete system crashes or instability, effectively denying legitimate users access to the communication services that the server provides. The specific nature of the flaw suggests that the server's RTMP parser lacks proper bounds checking and input sanitization mechanisms that would normally be expected in robust network protocol implementations.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire communication infrastructure that relies on the Flash Communication Server. Organizations using this server for real-time applications, such as online gaming platforms, collaborative workspaces, or live streaming services, could face significant downtime and service degradation. The vulnerability's exploitation does not require authentication or specialized privileges, making it particularly dangerous as it can be triggered by any attacker with network access to the server. This makes the vulnerability suitable for both accidental and intentional exploitation, with potential for widespread disruption across multiple users and applications. The fact that the vulnerability can be demonstrated against alpha builds of Flash Player 8.5 indicates that it represents a fundamental design flaw in the server's protocol handling rather than a specific implementation issue that might be limited to particular versions. This characteristic suggests that the vulnerability could affect not only the specific server versions mentioned but potentially other systems with similar RTMP implementations, creating a broader attack surface.
Mitigation strategies for this vulnerability should focus on implementing robust input validation and sanitization mechanisms throughout the RTMP processing pipeline. Organizations should immediately apply any available patches or updates from Macromedia/Microsoft that address this specific validation issue. Network-level protections such as firewalls and intrusion detection systems can help filter out malformed RTMP traffic, though these measures are not foolproof against all exploitation vectors. The implementation of proper bounds checking and input sanitization should be enforced at multiple layers of the system architecture, including protocol parsing, data handling, and memory management components. Additionally, monitoring and logging mechanisms should be enhanced to detect unusual RTMP traffic patterns that might indicate attempted exploitation. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to denial of service and protocol manipulation, and defensive measures should incorporate both preventive controls and detection capabilities. The vulnerability serves as a reminder of the critical importance of proper input validation in network services and the potential consequences when such validation is insufficient. Organizations should also consider implementing redundancy and failover mechanisms to minimize the impact of potential exploitation attempts on their communication services.