CVE-2011-0939 in IOS XE
Summary
by MITRE
Unspecified vulnerability in Cisco IOS 12.4, 15.0, and 15.1, and IOS XE 2.5.x through 3.2.x, allows remote attackers to cause a denial of service (device reload) via a crafted SIP message, aka Bug ID CSCth03022.
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Analysis
by VulDB Data Team • 11/21/2021
Cisco IOS versions 12.4, 15.0, and 15.1 along with IOS XE versions 2.5.x through 3.2.x contain an unspecified vulnerability that enables remote attackers to trigger a denial of service condition resulting in device reloads through the manipulation of SIP messages. This vulnerability specifically affects the Session Initiation Protocol implementation within the operating system and has been documented under Bug ID CSCth03022. The flaw resides in how the system processes incoming SIP messages, particularly those containing malformed or crafted parameters that cause the device to crash and subsequently reload its operating system. The vulnerability represents a critical security weakness that can be exploited without authentication, making it particularly dangerous in network environments where SIP traffic is processed by affected Cisco devices.
The technical nature of this vulnerability stems from inadequate input validation within the SIP processing module of Cisco IOS. When a maliciously crafted SIP message is received by an affected device, the system fails to properly sanitize or reject the malformed data before attempting to process it. This leads to a memory corruption condition or stack overflow that causes the device to become unstable and eventually reboot. The vulnerability is classified under CWE-122 as insufficient input validation, which directly relates to the improper handling of user-supplied data within the SIP parser. The attack vector is remote and requires no credentials to execute, making it particularly attractive to threat actors seeking to disrupt network services.
The operational impact of this vulnerability extends beyond simple service disruption as it can result in complete network outages when critical infrastructure devices such as routers, firewalls, or gateways are affected. Organizations relying on SIP for voice communications, video conferencing, or unified communications may experience significant business disruption when devices reload unexpectedly. The vulnerability affects Cisco devices that process SIP traffic, including voice gateways, routers with SIP functionality, and network security appliances that handle SIP signaling. The automatic device reload creates a cascading effect that can impact multiple services depending on the device's role within the network architecture.
Mitigation strategies for this vulnerability should include immediate deployment of Cisco's security patches and software updates that address the SIP processing flaw. Network administrators should implement SIP message filtering and validation at network boundaries to prevent malicious traffic from reaching affected devices. The implementation of access control lists and rate limiting on SIP traffic can help reduce the attack surface. Additionally, monitoring systems should be configured to detect unusual device reload patterns that may indicate exploitation attempts. Organizations should also consider implementing network segmentation to isolate SIP traffic and limit the potential impact of successful attacks. This vulnerability aligns with ATT&CK technique T1499.004 for network denial of service and represents a significant risk to network availability as outlined in the NIST Cybersecurity Framework.