CVE-2016-6441 in IOS XE
Summary
by MITRE
A vulnerability in the Transaction Language 1 (TL1) code of Cisco ASR 900 Series routers could allow an unauthenticated, remote attacker to cause a reload of, or remotely execute code on, the affected system. This vulnerability affects Cisco ASR 900 Series Aggregation Services Routers (ASR902, ASR903, and ASR907) that are running the following releases of Cisco IOS XE Software: 3.17.0S 3.17.1S 3.17.2S 3.18.0S 3.18.1S. More Information: CSCuy15175. Known Affected Releases: 15.6(1)S 15.6(2)S. Known Fixed Releases: 15.6(1)S2.12 15.6(1.17)S0.41 15.6(1.17)SP 15.6(2)SP 16.4(0.183) 16.5(0.10).
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2016-6441 represents a critical security flaw within the Transaction Language 1 implementation of Cisco ASR 900 Series routers, specifically affecting the ASR902, ASR903, and ASR907 models. This weakness resides in the handling of TL1 commands within the Cisco IOS XE Software operating on these aggregation services routers, creating a pathway for remote exploitation without requiring authentication credentials. The vulnerability stems from insufficient input validation and improper error handling mechanisms within the TL1 processing code, which allows attackers to craft malicious TL1 commands that can trigger unexpected behavior in the router's operational environment. The affected software versions include specific releases of Cisco IOS XE Software such as 3.17.0S through 3.18.1S and the corresponding 15.6(1)S and 15.6(2)S releases, making these systems particularly susceptible to exploitation.
The technical exploitation of this vulnerability manifests through the manipulation of TL1 protocol messages that are typically used for network management and configuration operations. When an attacker sends specially crafted TL1 commands to the vulnerable router, the system's failure to properly validate these inputs can result in memory corruption or arbitrary code execution within the router's processing environment. This flaw operates at the application layer of the network stack and leverages the inherent trust placed in legitimate TL1 management interfaces, allowing attackers to bypass traditional authentication mechanisms. The vulnerability's impact extends beyond simple denial of service, as it can enable complete system compromise through remote code execution, potentially allowing attackers to gain full control over the affected router's operations and access to connected network segments.
The operational implications of this vulnerability are severe for network infrastructure security, as it provides attackers with the capability to perform unauthorized system reloads or execute arbitrary code on critical network equipment. This vulnerability directly impacts the availability, integrity, and confidentiality of network services, as compromised routers can be used to disrupt network operations, redirect traffic, or serve as stepping stones for further attacks within the network infrastructure. The vulnerability's remote exploitability without authentication means that attackers can target these systems from anywhere on the internet, making it particularly dangerous for organizations that do not properly segment their network management interfaces or implement adequate monitoring controls. Organizations utilizing these specific router models and software versions face significant risk of unauthorized access to their core network infrastructure, potentially leading to widespread service disruption or data breaches.
Mitigation strategies for CVE-2016-6441 should prioritize the immediate implementation of software updates to the fixed releases including 15.6(1)S2.12, 15.6(1.17)S0.41, 15.6(1.17)SP, 15.6(2)SP, 16.4(0.183), and 16.5(0.10), which contain the necessary patches to address the TL1 processing vulnerabilities. Network administrators should also implement network segmentation to isolate management interfaces from public networks and apply access control lists to restrict TL1 protocol traffic to trusted management stations only. Additional defensive measures include disabling TL1 protocol functionality when not required, implementing comprehensive network monitoring to detect anomalous TL1 traffic patterns, and establishing regular vulnerability assessments to identify other potential weaknesses in network infrastructure. The vulnerability aligns with CWE-121, which describes buffer overflow conditions, and relates to ATT&CK technique T1210 for exploitation of remote services, emphasizing the need for both patch management and network security controls to effectively address this threat.