CVE-2013-1195 in Firewall Services Module
Summary
by MITRE
The time-based ACL implementation on Cisco Adaptive Security Appliances (ASA) devices, and in Cisco Firewall Services Module (FWSM), does not properly handle periodic statements for the time-range command, which allows remote attackers to bypass intended access restrictions by sending network traffic during denied time periods, aka Bug IDs CSCuf79091 and CSCug45850.
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Analysis
by VulDB Data Team • 05/03/2017
The vulnerability identified as CVE-2013-1195 affects Cisco Adaptive Security Appliances and Firewall Services Module devices, representing a critical flaw in the time-based access control list implementation. This weakness stems from improper handling of periodic statements within the time-range command functionality, creating a fundamental security gap in network access controls. The flaw specifically impacts the enforcement mechanism that should restrict network access during designated time periods, allowing malicious actors to circumvent these temporal restrictions through carefully crafted network traffic.
The technical implementation flaw resides in how the ASA and FWSM devices process time-range configurations that include periodic statements. When administrators configure time-based access controls using the time-range command with periodic scheduling, the devices fail to correctly evaluate whether traffic should be permitted or denied during specific time windows. This misimplementation enables attackers to send network traffic during periods when access should be denied, effectively bypassing the intended security controls that rely on temporal access restrictions. The vulnerability manifests as a logic error in the time-range evaluation engine, where periodic time periods are not properly validated against incoming network traffic.
The operational impact of this vulnerability is significant as it undermines the fundamental security model of time-based access controls that organizations rely upon for network protection. Attackers can exploit this weakness to gain unauthorized access to network resources during scheduled maintenance windows, administrative periods, or other time-restricted access periods. This bypass capability can be particularly dangerous when combined with other attack vectors, as it allows threat actors to operate within network perimeters during times when they might otherwise be restricted, potentially enabling extended access windows for malicious activities. The vulnerability affects organizations that depend on temporal access controls as part of their security posture, including those implementing time-based network segmentation or compliance requirements.
Organizations should implement immediate mitigations including disabling time-range functionality until proper patches are applied, implementing additional monitoring controls to detect unauthorized access during time-restricted periods, and reviewing existing access control policies to ensure alternative security measures are in place. Cisco has released patches addressing this vulnerability through security advisories that should be applied immediately to affected devices. The flaw aligns with CWE-284 Access Control Issues, specifically related to improper access control enforcement in time-based security mechanisms, and can be categorized under ATT&CK technique T1078 Valid Accounts for maintaining persistence through bypassed access controls. Network administrators should also consider implementing network segmentation strategies that do not rely on time-based access controls until the vulnerability is fully remediated and validated through proper testing procedures.