CVE-2007-6629 in Feng
Summary
by MITRE
Interpretation conflict in LScube Feng 0.1.15 and earlier allows remote attackers to cause a denial of service (NULL dereference and daemon crash) via a User-Agent header line that contains a carriage-return character, which is considered a line delimiter when the header is split into individual lines, but not when log_user_agent in RTSP_utils.c parses the content of the User-Agent line.
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Analysis
by VulDB Data Team • 07/30/2021
The vulnerability identified as CVE-2007-6629 represents a critical interpretation conflict within the LScube Feng streaming media server version 0.1.15 and earlier. This flaw manifests as a denial of service condition that can be triggered remotely through manipulation of the User-Agent HTTP header field. The vulnerability stems from inconsistent handling of carriage-return characters within different parsing contexts of the same data stream, creating a scenario where the same input produces divergent interpretations during processing phases.
The technical root cause lies in the dual interpretation of carriage-return characters within the RTSP_utils.c source file. When the server processes HTTP headers and splits them into individual lines, the carriage-return character is properly recognized as a line delimiter, effectively terminating the User-Agent header value. However, during subsequent parsing operations where the log_user_agent function processes the User-Agent content, the same carriage-return character is not treated as a line delimiter, leading to inconsistent state management. This discrepancy creates a NULL pointer dereference condition when the daemon attempts to process the malformed header value.
The operational impact of this vulnerability is severe as it enables remote attackers to crash the LScube Feng daemon through carefully crafted HTTP requests. The attack requires only a single malformed User-Agent header containing a carriage-return character, making it easily exploitable across network boundaries. Once triggered, the daemon experiences a NULL dereference that results in an immediate crash, causing a denial of service condition that disrupts legitimate streaming services and potentially affects other connected systems relying on the media server functionality.
This vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions, and demonstrates characteristics consistent with CWE-707, representing improper handling of input data that leads to unexpected program behavior. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 which covers network denial of service attacks, and T1595.001 which involves reconnaissance activities to identify system weaknesses. The attack vector operates at the application layer and requires no authentication, making it particularly dangerous in environments where media streaming services are exposed to untrusted network traffic.
The recommended mitigation strategy involves implementing input validation and sanitization for all HTTP headers, particularly the User-Agent field, to normalize carriage-return and line-feed characters before processing. System administrators should upgrade to version 0.1.16 or later where this interpretation conflict has been resolved through consistent handling of delimiter characters. Additionally, deploying intrusion detection systems that monitor for unusual User-Agent header patterns can provide early warning of potential exploitation attempts. Network segmentation and access control measures should be implemented to limit exposure of vulnerable systems to untrusted networks, while regular security audits should verify proper implementation of header parsing logic to prevent similar interpretation conflicts in other components.