CVE-2012-0362 in IOS
Summary
by MITRE
The extended ACL functionality in Cisco IOS 12.2(58)SE2 and 15.0(1)SE discards all lines that end with a log or time keyword, which allows remote attackers to bypass intended access restrictions in opportunistic circumstances by sending network traffic, aka Bug ID CSCts01106.
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Analysis
by VulDB Data Team • 05/09/2018
The vulnerability described in CVE-2012-0362 represents a critical flaw in Cisco IOS software that affects versions 12.2(58)SE2 and 15.0(1)SE. This issue specifically targets the extended access control list (ACL) functionality, which serves as a fundamental security mechanism for network traffic filtering and access control. The flaw manifests when ACL rules contain log or time keywords at the end of their definitions, causing the entire rule to be discarded by the IOS processing engine. This behavior fundamentally undermines the security posture of affected Cisco devices by creating a bypass mechanism that allows unauthorized network access.
The technical implementation of this vulnerability stems from how Cisco IOS processes extended ACL entries containing specific keywords. When the system encounters an ACL rule ending with either the log or time keyword, the IOS software fails to properly parse and execute the rule, effectively removing it from the active access control configuration. This creates a scenario where administrators believe certain access restrictions are in place, while the corresponding rules are silently ignored. The vulnerability operates at the packet processing layer of the IOS kernel, making it particularly dangerous as it affects the core network filtering mechanisms that protect against unauthorized access attempts.
From an operational perspective, this vulnerability creates a significant security risk for organizations relying on Cisco IOS devices for network segmentation and access control. Attackers can exploit this flaw by crafting network traffic that triggers the discarded rule behavior, potentially bypassing firewall restrictions and gaining unauthorized access to protected network segments. The opportunistic nature of this vulnerability means that exploitation does not require highly sophisticated techniques, making it particularly dangerous in environments where network traffic patterns can be easily monitored and manipulated. The impact extends beyond simple access bypass as it can lead to complete network compromise when combined with other vulnerabilities or attack vectors.
The security implications of CVE-2012-0362 align with CWE-119, which addresses memory access violations and improper handling of input data. This vulnerability also maps to ATT&CK technique T1046, which involves network service scanning and reconnaissance activities that can be facilitated by bypassing access controls. Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Cisco security patches, reviewing and reconfiguring ACL rules to avoid problematic keyword combinations, and monitoring network traffic for unusual patterns that might indicate exploitation attempts. Additionally, network administrators should consider implementing redundant access control mechanisms and conducting thorough security assessments to identify any potential unauthorized access that may have occurred during the vulnerability's active period. The incident highlights the critical importance of proper input validation and the potential for seemingly minor parsing issues to create significant security weaknesses in network infrastructure devices.