CVE-2006-0738 in softphone
Summary
by MITRE
Multiple format string vulnerabilities in eStara SIP softphone allow remote attackers to cause a denial of service (hang) via SIP INVITE requests with format string specifiers in the SDP session description, as demonstrated using (1) the field name, (2) the o field (owner/creator and session identifier), or (3) the m field (media name and transport address).
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Analysis
by VulDB Data Team • 03/16/2025
The vulnerability identified as CVE-2006-0738 represents a critical format string vulnerability within the eStara SIP softphone implementation that exposes systems to remote denial of service attacks through carefully crafted SIP INVITE requests. This vulnerability specifically targets the Session Description Protocol (SDP) parsing functionality where the softphone fails to properly validate and sanitize input data before processing format specifiers. The attack vector leverages the inherent risks associated with improper input handling in network protocol implementations, where malicious actors can inject format string specifiers that trigger unexpected behavior in the application's string processing routines.
The technical flaw manifests in the software's handling of three distinct SDP fields during SIP INVITE processing. The first vulnerable field is the field name itself, where attackers can inject format specifiers that cause the application to misinterpret the intended session description. The second vulnerable component is the o field, which contains the owner/creator and session identifier information, where malicious format specifiers can disrupt the normal parsing flow. The third vulnerable field is the m field, which specifies the media name and transport address, where similar format string injection attacks can cause the application to crash or hang during processing. These vulnerabilities fall under CWE-134, which specifically addresses the use of format strings without proper validation, making them particularly dangerous as they can lead to arbitrary code execution or system instability.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can effectively render the affected SIP softphone unusable for legitimate communication while potentially providing attackers with opportunities to escalate their attack. When a remote attacker successfully exploits these format string vulnerabilities, the softphone application becomes unresponsive or crashes entirely, disrupting voice communication services for all users relying on that particular client. The attack can be executed without requiring authentication, making it particularly dangerous in environments where SIP softphones are deployed in enterprise or telecommunication networks. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1203, which involves the exploitation of system vulnerabilities to gain access to services or applications, and T1499, which covers network disruption attacks that can be used to deny service to legitimate users.
Mitigation strategies for CVE-2006-0738 must address both immediate defensive measures and long-term architectural improvements. Organizations should implement network segmentation and access controls to limit exposure to potentially vulnerable SIP softphone implementations, while also applying vendor-specific patches or updates when available. The software should be configured to validate all incoming SDP data against strict format requirements, rejecting any input containing potentially dangerous format specifiers. Additionally, implementing intrusion detection systems that can identify and block suspicious SIP INVITE patterns can provide an additional layer of protection. From a compliance standpoint, this vulnerability demonstrates the importance of adhering to security standards such as those outlined in the NIST Cybersecurity Framework, particularly in the areas of vulnerability management and secure software development practices. Organizations should also consider implementing application-level firewalls or proxies that can sanitize SIP traffic before it reaches the vulnerable softphone applications, thereby reducing the attack surface and preventing exploitation of these format string vulnerabilities.