CVE-2011-0946 in IOS
Summary
by MITRE
The NAT implementation in Cisco IOS 12.1 through 12.4 and 15.0 through 15.1, and IOS XE 3.1.xSG, allows remote attackers to cause a denial of service (device reload or hang) via malformed NetMeeting Directory (aka Internet Locator Service or ILS) LDAP traffic, aka Bug ID CSCtd10712.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 11/21/2021
The vulnerability described in CVE-2011-0946 represents a critical denial of service flaw within Cisco IOS network operating systems that affects multiple versions including 12.1 through 12.4, 15.0 through 15.1, and IOS XE 3.1.xSG releases. This issue specifically targets the Network Address Translation implementation which serves as a fundamental component for managing network traffic between internal and external networks. The vulnerability manifests when the system receives malformed NetMeeting Directory traffic, also known as Internet Locator Service or ILS LDAP traffic, which is typically used for directory services in Microsoft environments. The flaw allows remote attackers to exploit this weakness without requiring authentication or specialized privileges, making it particularly dangerous in network environments where such traffic might traverse untrusted boundaries.
The technical nature of this vulnerability stems from insufficient input validation within the IOS NAT processing engine when handling specific LDAP packet structures used by the NetMeeting Directory service. When the system encounters malformed ILS LDAP traffic, the parsing logic fails to properly handle the malformed data structures, leading to unpredictable behavior within the network processing modules. This improper handling causes the device to either reload automatically or become unresponsive, effectively rendering the network infrastructure unavailable to legitimate users. The vulnerability operates at the network protocol level where the IOS NAT implementation fails to properly sanitize incoming LDAP traffic before processing it through the translation mechanisms, creating a path for malicious actors to trigger system instability through crafted network packets.
The operational impact of this vulnerability extends beyond simple service disruption as it can affect entire network segments that rely on NAT functionality for connectivity. Network administrators may experience unexpected device outages that require manual intervention to restore services, potentially causing business disruption and requiring emergency response procedures. The attack vector is particularly concerning because it operates over standard network protocols that are commonly allowed through firewalls and security devices, making it difficult to detect and prevent through traditional network monitoring approaches. Organizations that have not patched their IOS systems remain vulnerable to automated attacks that could systematically target multiple devices across their network infrastructure, potentially causing cascading failures in network connectivity.
Mitigation strategies for this vulnerability require immediate patching of affected IOS versions with the appropriate security updates provided by Cisco. Network administrators should also implement network segmentation and access control measures to limit exposure to potentially malicious LDAP traffic, particularly from untrusted network segments. The implementation of traffic filtering rules to block ILS LDAP traffic at network perimeters can provide additional protection layers while patches are being deployed. Organizations should also consider monitoring network traffic for unusual patterns of LDAP communication that might indicate exploitation attempts. From a compliance perspective, this vulnerability aligns with CWE-129 and CWE-772 categories related to input validation and resource management, and it maps to ATT&CK technique T1499.004 for network denial of service attacks. The vulnerability demonstrates the importance of maintaining up-to-date network security infrastructure and implementing robust patch management procedures to prevent exploitation of known weaknesses in network operating systems.