CVE-2006-0737 in softphone
Summary
by MITRE
eStara SIP softphone allows remote attackers to cause a denial of service (crash) via a SIP OPTIONS request with a negative Expires field.
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Analysis
by VulDB Data Team • 03/20/2025
The vulnerability identified as CVE-2006-0737 affects the eStara SIP softphone implementation, presenting a significant denial of service risk that stems from improper handling of SIP protocol messages. This flaw specifically manifests when the softphone receives a SIP OPTIONS request containing a negative value in the Expires header field, which triggers an unexpected crash in the application. The issue represents a classic buffer overflow or input validation vulnerability that exploits the software's failure to properly sanitize incoming SIP protocol data, creating a condition where malformed requests can disrupt normal service operations.
From a technical perspective, the vulnerability operates at the application layer of the SIP protocol stack, specifically targeting the parsing and processing logic within the eStara softphone client. When the software encounters a SIP OPTIONS message with a negative Expires value, it fails to validate the input properly and attempts to process this invalid data, leading to memory corruption or execution flow disruption. This behavior aligns with CWE-129, which describes improper validation of length fields, and CWE-125, which covers out-of-bounds read conditions. The vulnerability demonstrates how seemingly benign protocol fields can be weaponized to cause system instability when proper input validation mechanisms are absent or insufficient.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by remote attackers without requiring authentication or privileged access to the system. An attacker can simply send a crafted SIP OPTIONS request with a negative Expires field to any target running the vulnerable eStara softphone, causing the application to crash and potentially requiring system restart or manual intervention to restore service. This makes the vulnerability particularly dangerous in environments where SIP softphones are used for critical communications, as it can be leveraged to create persistent availability issues that may affect business operations or emergency communication systems.
The attack surface for this vulnerability includes any network endpoint that accepts SIP OPTIONS requests from external sources, particularly in enterprise communication environments where softphones are deployed across various network segments. According to ATT&CK framework category T1499, this represents a denial of service attack technique that targets network services and can be classified under T1595 for reconnaissance activities that identify vulnerable systems. The vulnerability also relates to T1071, which covers application layer protocol usage, as it exploits the legitimate SIP protocol mechanisms to achieve malicious outcomes. Organizations using eStara softphones should consider implementing network segmentation, SIP protocol filtering, and monitoring solutions to detect and prevent exploitation attempts.
Mitigation strategies should focus on both immediate patching and operational controls to address the vulnerability effectively. The primary solution involves applying vendor-provided security updates that implement proper input validation for SIP Expires header fields, ensuring that negative values are either rejected or handled gracefully without causing application crashes. Network-level defenses should include SIP protocol filtering rules that prevent malformed OPTIONS requests from reaching vulnerable endpoints, while also implementing rate limiting to prevent abuse of the service. Additionally, system administrators should establish monitoring procedures to detect unusual patterns of SIP traffic that may indicate exploitation attempts, and maintain incident response procedures for rapid recovery when attacks occur. Organizations should also consider implementing intrusion detection systems specifically tuned to detect SIP protocol anomalies that could indicate exploitation of this or similar vulnerabilities in their communication infrastructure.