CVE-2010-4687 in IOS
Summary
by MITRE
STCAPP (aka the SCCP telephony control application) on Cisco IOS before 15.0(1)XA1 does not properly handle multiple calls to a shared line, which allows remote attackers to cause a denial of service (port hang) by simultaneously ending two calls that were controlled by CallManager Express (CME), aka Bug ID CSCtd42552.
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Analysis
by VulDB Data Team • 10/11/2021
The vulnerability described in CVE-2010-4687 affects Cisco IOS versions prior to 15.0(1)XA1 and specifically targets the STCAPP component, also known as the SCCP telephony control application. This flaw exists within the CallManager Express (CME) implementation that manages telephony services on Cisco routers and switches. The vulnerability manifests when multiple calls are placed on a shared line and the system fails to properly manage concurrent call termination events, creating a condition where the port becomes unresponsive and enters a state of permanent hang. This represents a critical denial of service vulnerability that directly impacts telephony infrastructure and network availability.
The technical root cause of this vulnerability lies in the improper handling of concurrent call termination operations within the STCAPP module. When two calls are simultaneously ended on a shared line that is managed by CallManager Express, the system's call control logic fails to properly coordinate the cleanup operations. This leads to a race condition where the port management structures become corrupted or locked in an inconsistent state. The flaw specifically affects the SCCP (Skinny Client Control Protocol) implementation that Cisco uses for telephony control, which is part of the broader telephony subsystem that handles voice communication services. According to CWE classification, this vulnerability maps to CWE-362, which describes a race condition error that can lead to improper resource handling and system instability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire telephony networks that rely on Cisco IOS devices. When a port hangs due to this vulnerability, it effectively removes the associated telephony line from service until manual intervention occurs through device reboot or administrative reset procedures. This can severely impact business continuity for organizations that depend on voice communication services, particularly in mission-critical environments where phone availability is essential for operations. The vulnerability is particularly dangerous because it can be exploited remotely without authentication, making it accessible to attackers who may not require physical access to the network infrastructure. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving denial of service and system compromise, potentially enabling further attacks through network disruption.
Mitigation strategies for CVE-2010-4687 primarily involve upgrading to Cisco IOS version 15.0(1)XA1 or later, which contains the necessary patches to address the concurrent call handling issue. Network administrators should also implement monitoring solutions that can detect port hang conditions and automatically alert administrators to potential exploitation attempts. Additional defensive measures include configuring proper call admission control to limit concurrent call scenarios on shared lines, implementing redundant telephony paths where possible, and establishing automated recovery procedures for affected ports. The vulnerability highlights the importance of proper resource management in telephony applications and demonstrates how seemingly simple race conditions in call control logic can lead to significant service disruptions. Organizations should also conduct regular security assessments of their telephony infrastructure to identify similar vulnerabilities in other network components that may be susceptible to similar race condition flaws.