CVE-2007-0248 in Squid
Summary
by MITRE
The aclMatchExternal function in Squid before 2.6.STABLE7 allows remote attackers to cause a denial of service (crash) by causing an external_acl queue overload, which triggers an infinite loop.
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Analysis
by VulDB Data Team • 07/14/2019
The vulnerability identified as CVE-2007-0248 affects the Squid caching proxy software, specifically within the aclMatchExternal function that handles external access control list processing. This flaw represents a classic denial of service vulnerability that can be exploited by remote attackers to disrupt service availability. The issue manifests when external acl queues become overloaded, creating conditions that trigger an infinite loop within the software's processing logic. Such a scenario fundamentally undermines the stability and reliability of the proxy service, potentially affecting all users relying on the caching infrastructure.
The technical implementation of this vulnerability stems from inadequate queue management and loop termination logic within the aclMatchExternal function. When external acl requests exceed the system's processing capacity, the queue becomes overwhelmed with pending operations that cannot be properly handled due to flawed loop conditions. This condition creates a scenario where the system enters an infinite processing loop, consuming excessive CPU resources and ultimately causing the Squid service to crash or become unresponsive. The vulnerability operates at the application layer and requires no authentication or specialized privileges to exploit, making it particularly dangerous in production environments where continuous service availability is critical.
The operational impact of CVE-2007-0248 extends beyond simple service disruption to potentially compromise entire network infrastructures that depend on Squid for caching and proxy services. Organizations utilizing affected Squid versions face the risk of extended downtime, degraded network performance, and potential cascading failures in systems that rely on consistent proxy functionality. The vulnerability's remote exploitability means that attackers can trigger the denial of service condition from any network location without requiring physical access or elevated privileges. This characteristic aligns with attack patterns documented in the MITRE ATT&CK framework under the service stoppage and resource exhaustion tactics, where adversaries target application-level vulnerabilities to disrupt system availability.
Mitigation strategies for this vulnerability primarily focus on immediate software updates to versions that address the specific queue handling and loop termination issues. Organizations should prioritize upgrading to Squid 2.6.STABLE7 or later releases where the flaw has been resolved through improved queue management and robust loop detection mechanisms. Additionally, implementing proper queue monitoring and resource limits can help detect and prevent the conditions that lead to the infinite loop scenario. Network administrators should consider deploying intrusion detection systems that can identify unusual queue behavior patterns and implement rate limiting for external acl requests to prevent overload conditions. The vulnerability demonstrates the importance of proper input validation and queue management practices that align with CWE guidelines for preventing resource exhaustion and infinite loop conditions in software applications.