CVE-2016-3947 in Squid
Summary
by MITRE
Heap-based buffer overflow in the Icmp6::Recv function in icmp/Icmp6.cc in the pinger utility in Squid before 3.5.16 and 4.x before 4.0.8 allows remote servers to cause a denial of service (performance degradation or transition failures) or write sensitive information to log files via an ICMPv6 packet.
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Analysis
by VulDB Data Team • 07/12/2022
The vulnerability described in CVE-2016-3947 represents a critical heap-based buffer overflow affecting the Squid proxy server's pinger utility. This flaw exists within the Icmp6::Recv function located in icmp/Icmp6.cc, specifically impacting versions prior to 3.5.16 and 4.x prior to 4.0.8. The vulnerability arises from inadequate input validation when processing ICMPv6 packets, creating a condition where remote attackers can manipulate the system through crafted malicious packets. The buffer overflow occurs in the heap memory region, making it particularly dangerous as it can lead to unpredictable behavior and system instability.
The technical implementation of this vulnerability stems from improper bounds checking during ICMPv6 packet processing. When the pinger utility receives an ICMPv6 packet, the Icmp6::Recv function fails to properly validate the packet size or structure before attempting to copy data into allocated buffer space. This classic buffer overflow condition allows attackers to write beyond the allocated memory boundaries, potentially overwriting adjacent memory locations. The vulnerability manifests through the icmp/Icmp6.cc module's handling of ICMPv6 responses, where the system's failure to enforce proper buffer limits creates opportunities for exploitation. The flaw can be categorized under CWE-121 as a stack-based buffer overflow, though the heap-based nature makes it particularly challenging to predict and control.
The operational impact of this vulnerability extends beyond simple denial of service to include potential information disclosure and system performance degradation. Remote attackers can leverage this vulnerability to cause performance degradation through memory corruption, leading to system instability and potential transitions failures within the Squid proxy infrastructure. Additionally, the overflow may result in sensitive information being written to log files, creating potential data leakage scenarios that could expose system internals or user data. The pinger utility's role in network monitoring and connectivity testing makes this vulnerability particularly dangerous as it can be exploited to disrupt critical network services. Attackers can repeatedly send malicious ICMPv6 packets to trigger the overflow condition, potentially leading to sustained performance degradation or complete service unavailability.
Mitigation strategies for CVE-2016-3947 require immediate patching of affected Squid versions to the recommended secure releases. Organizations should prioritize updating their Squid proxy implementations to versions 3.5.16 or 4.0.8 and later, which contain the necessary fixes for the buffer overflow condition. Network administrators should also implement additional monitoring and logging to detect anomalous ICMPv6 traffic patterns that might indicate exploitation attempts. The vulnerability's characteristics align with ATT&CK technique T1071.004 for application layer protocol: dns and T1499.004 for network disruption, making defensive measures crucial for maintaining network integrity. System hardening measures including input validation enforcement and memory protection mechanisms should be implemented alongside the patching process. Organizations should also consider implementing network segmentation and access controls to limit exposure of vulnerable Squid instances to untrusted networks, as the vulnerability's remote nature makes it particularly attractive to attackers seeking to exploit proxy server configurations.