CVE-2007-4461 in NuFW
Summary
by MITRE
NuFW 2.2.3, and certain other versions after 2.0, allows remote attackers to bypass time-based packet filtering rules via certain "out of period" choices of packet transmission time.
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Analysis
by VulDB Data Team • 09/07/2018
The vulnerability described in CVE-2007-4461 affects NuFW version 2.2.3 and subsequent releases following version 2.0, representing a significant flaw in network packet filtering mechanisms. This issue resides within the time-based packet filtering functionality that is commonly implemented in firewall and network security appliances to control traffic based on temporal criteria. The vulnerability specifically targets the logic that governs how packets are evaluated against time-based rules, creating a potential bypass mechanism that could allow malicious actors to circumvent security controls.
The technical flaw manifests when packets are transmitted outside of the designated time periods specified in the firewall rules, yet the system incorrectly processes these packets as if they were within the allowed time windows. This occurs due to improper handling of packet transmission timing within the filtering engine, where the system fails to properly validate the temporal context of incoming traffic against configured time-based restrictions. The vulnerability exploits a gap in the rule evaluation process that allows packets to be accepted even when their transmission times fall outside the specified operational periods, effectively neutralizing time-based access controls.
From an operational perspective, this vulnerability creates a serious security risk as it enables remote attackers to bypass time-based network restrictions that are typically implemented to limit access during specific hours or days. Network administrators might configure time-based rules to restrict access to sensitive systems during off-hours or to implement maintenance windows, but this flaw allows unauthorized access regardless of these temporal controls. The impact extends beyond simple access bypass, as it undermines the fundamental principle of time-based network security policies that many organizations rely upon for compliance and risk mitigation purposes.
The vulnerability aligns with CWE-284, which addresses improper access control mechanisms in network security systems, and demonstrates how temporal access controls can be circumvented through flawed implementation logic. From an adversarial perspective, this issue maps to ATT&CK technique T1071.004, which covers application layer protocol: DNS, as attackers could leverage this bypass to conduct time-based attacks during restricted periods when monitoring might be less active. The flaw particularly affects organizations that depend on time-based filtering for regulatory compliance, such as those in financial services or healthcare sectors where access controls must be strictly enforced during specific operational windows.
Mitigation strategies should include immediate patching of affected NuFW versions to address the time-based filtering logic flaw, implementing additional monitoring of time-based rule violations, and considering alternative access control mechanisms that do not rely solely on temporal parameters. Organizations should also review their current time-based filtering policies to ensure proper validation of packet timing and consider implementing redundant access controls that can detect and prevent such bypass attempts. Network segmentation and layered security approaches become critical when time-based controls are compromised, as they provide additional defense-in-depth measures that can compensate for the vulnerability in the primary filtering mechanism.