CVE-2023-49286 in Squid
Summary
by MITRE • 12/05/2023
Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Due to an Incorrect Check of Function Return Value bug Squid is vulnerable to a Denial of Service attack against its Helper process management. This bug is fixed by Squid version 6.5. Users are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 05/16/2025
The vulnerability identified as CVE-2023-49286 affects Squid caching proxy software, a widely deployed web proxy solution that supports multiple protocols including HTTP, HTTPS, and FTP. This security flaw resides within the Helper process management functionality of Squid, representing a critical weakness that can be exploited to disrupt service availability. The vulnerability manifests as an incorrect check of function return values, a pattern that falls under the well-documented CWE-252 weakness category, which specifically addresses issues where programs fail to properly check return values from functions. The flaw impacts the proxy's ability to manage its helper processes effectively, creating a potential avenue for malicious actors to compromise system availability.
The technical implementation of this vulnerability stems from insufficient validation of function return codes within Squid's helper process management code. When helper processes are invoked or managed, the software fails to properly verify whether these operations complete successfully. This oversight allows attackers to craft specific requests or conditions that cause helper processes to enter an inconsistent state, ultimately leading to a denial of service condition. The vulnerability specifically affects Squid versions prior to 6.5, making it a version-specific issue that has been addressed through proper code review and implementation of robust return value checking mechanisms. The absence of workarounds indicates that the flaw is deeply embedded in the process management logic rather than being a simple configuration issue.
The operational impact of CVE-2023-49286 extends beyond simple service disruption, potentially affecting organizations that rely heavily on Squid for web caching and proxy services. When exploited, this vulnerability can cause helper processes to terminate unexpectedly or become unresponsive, leading to complete service degradation for users relying on the proxy infrastructure. This type of denial of service attack aligns with ATT&CK technique T1499.004, which covers network denial of service attacks. Organizations using Squid for caching web traffic, content delivery, or network filtering may experience complete loss of proxy functionality, requiring manual intervention to restore services. The impact is particularly severe in environments where Squid serves as a critical infrastructure component for internet access or content filtering.
Security professionals should prioritize immediate upgrade to Squid version 6.5 or later to remediate this vulnerability, as no effective workarounds exist for the issue. The fix implemented in version 6.5 addresses the root cause by introducing proper function return value validation throughout the helper process management code. Organizations should conduct thorough testing of the updated version in their environments to ensure compatibility with existing configurations and policies. The vulnerability demonstrates the importance of proper input validation and error handling in critical system components, particularly those managing external processes that form the backbone of network infrastructure services. This flaw serves as a reminder of the potential consequences when basic programming practices such as return value checking are neglected in security-sensitive applications, highlighting the need for comprehensive code review processes and adherence to secure coding standards.