CVE-2007-2729 in Personal Firewall
Summary
by MITRE
Comodo Firewall Pro 2.4.18.184 and Comodo Personal Firewall 2.3.6.81, and probably older Comodo Firewall versions, do not properly test for equivalence of process identifiers for certain Microsoft Windows API functions in the NT kernel 5.0 and greater, which allows local users to call these functions, and bypass firewall rules or gain privileges, via a modified identifier that is one, two, or three greater than the canonical identifier.
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Analysis
by VulDB Data Team • 10/24/2017
The vulnerability described in CVE-2007-2729 represents a critical flaw in Comodo Firewall Pro and Personal Firewall versions 2.4.18.184 and 2.3.6.81 respectively, affecting Windows NT kernel versions 5.0 and greater. This issue stems from improper validation of process identifiers within the Windows API function calls, creating a security bypass mechanism that allows local attackers to circumvent firewall protections. The flaw specifically targets the kernel-level process identification mechanisms that are fundamental to Windows security model implementation. The vulnerability manifests when the firewall software fails to properly verify that process identifiers match exactly, instead accepting modified identifiers that are incremented by one, two, or three units from the canonical process identifier. This behavior creates a window of opportunity for privilege escalation and firewall rule bypass, as attackers can manipulate process identification numbers to gain unauthorized access to network resources. The impact is particularly severe because it operates at the kernel level where process identification is crucial for maintaining system security boundaries and access controls.
The technical implementation of this vulnerability involves a specific flaw in how Comodo firewall software validates process identifiers during Windows API function calls. When the firewall software processes API requests, it should validate that the calling process identifier exactly matches the expected canonical identifier for the operation. However, the flawed implementation accepts identifiers that are numerically close to the canonical values, specifically allowing identifiers that are one, two, or three greater than the expected value. This numerical tolerance creates a predictable pattern that attackers can exploit by crafting process identifiers that fall within this acceptable range. The vulnerability is particularly concerning because it operates within the NT kernel environment where process identification is fundamental to Windows security architecture. The flaw essentially creates a backdoor mechanism through which local users can bypass the normal access control checks that should prevent unauthorized network access or privilege escalation. This type of vulnerability falls under the category of improper input validation and weak access control mechanisms, which are commonly classified as CWE-20 (Improper Input Validation) and CWE-284 (Improper Access Control).
The operational impact of this vulnerability extends beyond simple firewall bypass to potentially enable privilege escalation attacks and unauthorized network access within the compromised system. Local attackers who can manipulate process identifiers to exploit this flaw can effectively circumvent the firewall protection mechanisms that are designed to prevent unauthorized access to network resources. This vulnerability allows attackers to execute functions that should be restricted to specific processes or users, potentially enabling them to perform administrative actions or access sensitive network services. The attack vector is particularly dangerous because it requires only local system access, making it more accessible than remote exploitation methods. The vulnerability's impact is amplified by its potential to allow attackers to gain elevated privileges, as the modified identifier approach can be used to bypass security checks that normally prevent privilege escalation. This flaw directly violates the principle of least privilege and can enable attackers to perform actions that should be restricted to authorized users or system processes. The vulnerability affects all Comodo Firewall versions up to the specified releases, indicating a widespread issue that could impact numerous systems in corporate and personal environments.
Mitigation strategies for this vulnerability should focus on immediate software updates and system hardening measures. The most effective immediate solution is to upgrade to newer versions of Comodo Firewall that address this specific validation flaw in process identifier handling. System administrators should also implement additional security controls including regular security audits of firewall configurations and monitoring for unusual process identification patterns. The vulnerability highlights the importance of proper input validation and access control mechanisms in security software implementations. Organizations should consider implementing additional logging and monitoring for API function calls that involve process identification to detect potential exploitation attempts. The flaw demonstrates the critical importance of rigorous testing of security software, particularly in kernel-level components where improper validation can create significant security risks. Security professionals should also consider implementing network segmentation and access control lists as additional protective measures to limit the impact of potential exploitation. This vulnerability serves as a reminder of the importance of adhering to security best practices and the potential consequences of inadequate validation mechanisms in security-critical software components. The issue aligns with ATT&CK techniques related to privilege escalation and defense evasion, where attackers can use such flaws to bypass security controls and maintain persistent access to systems.