CVE-2023-46847 in Squid Web Proxy
Summary
by MITRE • 11/03/2023
Squid is vulnerable to a Denial of Service, where a remote attacker can perform buffer overflow attack by writing up to 2 MB of arbitrary data to heap memory when Squid is configured to accept HTTP Digest Authentication.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 05/18/2025
The vulnerability identified as CVE-2023-46847 represents a critical buffer overflow condition within the Squid proxy server software that can be exploited to cause remote denial of service. This flaw specifically manifests when Squid is configured to accept HTTP Digest Authentication, making it particularly dangerous for organizations that rely on this authentication mechanism for their proxy infrastructure. The vulnerability stems from insufficient input validation and memory management practices within the authentication processing pipeline, where the software fails to properly constrain the amount of data that can be written to heap memory during digest authentication operations.
The technical exploitation of this vulnerability involves a remote attacker crafting malicious HTTP requests that contain excessive data payloads, specifically up to 2 megabytes of arbitrary data, which are then processed by the Squid server during authentication. When the server attempts to handle these oversized data inputs, it fails to implement proper bounds checking, allowing the attacker to overflow heap memory buffers and potentially cause memory corruption. This memory corruption can lead to unpredictable behavior including application crashes, memory exhaustion, or even potential exploitation for more advanced attack vectors. The vulnerability aligns with CWE-121, which categorizes heap-based buffer overflow conditions, and represents a classic example of improper input validation that can be leveraged for denial of service attacks.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect the entire proxy infrastructure of organizations relying on Squid for web filtering, caching, or authentication services. When exploited, the denial of service condition can result in complete unavailability of proxy services, affecting thousands of users who depend on the network infrastructure for internet access. Organizations may experience cascading failures as dependent services and applications lose connectivity through the compromised proxy. The vulnerability is particularly concerning because it requires minimal privileges to exploit and can be executed remotely without authentication, making it an attractive target for automated attack tools. According to ATT&CK framework, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1595.001, which involves reconnaissance techniques used to identify vulnerable systems.
Mitigation strategies for CVE-2023-46847 should prioritize immediate patching of affected Squid installations, as vendors have released security updates addressing the buffer overflow condition. Organizations should also implement network-level mitigations including firewall rules that restrict access to authentication endpoints and monitoring systems that can detect unusual data patterns in HTTP requests. Configuration hardening measures should include disabling HTTP Digest Authentication where possible and implementing proper input validation at the proxy level. Additionally, organizations should consider implementing intrusion detection systems that can identify exploitation attempts and establish baseline network behavior to quickly detect anomalous traffic patterns associated with this vulnerability. The remediation process should also include comprehensive testing of patched systems to ensure that the fix does not introduce compatibility issues with existing proxy configurations and authentication workflows.