CVE-2009-2534 in Helix Server
Summary
by MITRE
RealNetworks Helix Server and Helix Mobile Server before 13.0.0 allow remote attackers to cause a denial of service (daemon crash) via an RTSP SETUP request that (1) specifies the / URI or (2) lacks a / character in the URI.
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Analysis
by VulDB Data Team • 12/07/2024
The vulnerability identified as CVE-2009-2534 affects RealNetworks Helix Server and Helix Mobile Server versions prior to 13.0.0, representing a significant denial of service weakness in real-time streaming protocols. This flaw specifically targets the RTSP (Real Time Streaming Protocol) implementation within these media servers, where improper handling of SETUP requests can lead to complete daemon crashes and service unavailability. The vulnerability demonstrates a classic buffer overflow or parsing error condition that occurs when the server processes malformed URI specifications in RTSP communication.
The technical exploitation of this vulnerability occurs through carefully crafted RTSP SETUP requests that manipulate the Uniform Resource Identifier portion of the protocol message. Attackers can trigger the vulnerability by sending a SETUP request that either specifies the root URI path or omits the forward slash character from the URI entirely. This particular flaw exploits a parsing inconsistency in how the Helix Server handles URI normalization and validation, where the server fails to properly sanitize or validate incoming URI components before processing them. The absence of proper input validation creates an execution path where malformed URIs can cause memory corruption or stack overflow conditions that result in immediate daemon termination.
From an operational impact perspective, this vulnerability poses a substantial risk to organizations relying on RealNetworks streaming infrastructure, as it allows remote attackers to disrupt media services without requiring authentication or specialized privileges. The denial of service condition affects the entire streaming daemon, potentially impacting multiple concurrent users and causing widespread service interruption. This vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios, as the server's response to malformed URIs likely involves improper memory management during URI parsing operations. The attack vector operates entirely over the network without requiring physical access or user interaction, making it particularly dangerous for publicly accessible streaming servers.
The exploitation of this vulnerability directly maps to ATT&CK technique T1499.004, which covers network denial of service attacks through manipulation of network services. Organizations implementing RealNetworks Helix Server solutions should prioritize immediate patching to version 13.0.0 or later, as this represents the first release containing the necessary fixes for the URI parsing vulnerability. Additionally, network segmentation and firewall rules should be implemented to restrict RTSP traffic to trusted sources only, while monitoring systems should be configured to detect anomalous RTSP SETUP request patterns. The mitigation strategy should include input validation enforcement, where all incoming URI components are normalized and validated before processing, and implementing rate limiting mechanisms to prevent abuse of the vulnerable endpoint. Organizations should also consider deploying intrusion detection systems capable of identifying and blocking malicious RTSP SETUP requests based on known signature patterns associated with this vulnerability.