Overview
Squid, a widely used caching proxy for the web, suffers from a severe vulnerability in versions 6.3 and below. This vulnerability, designated as CVE-2025-54574, can potentially lead to a heap buffer overflow and even remote code execution attacks. This vulnerability is particularly concerning because of Squid’s widespread use in caching and forwarding web requests, making it a critical component in many network infrastructures. Thus, a successful exploit can have far-reaching consequences, including system compromise and data leakage.
Vulnerability Summary
CVE ID: CVE-2025-54574
Severity: Critical (CVSS 9.3)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System Compromise, Data Leakage
Affected Products
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Product | Affected Versions
Squid | 6.3 and below
How the Exploit Works
The vulnerability stems from incorrect buffer management within Squid when processing URN (Uniform Resource Names). If a malicious actor sends a specially crafted URN to a vulnerable Squid server, it can cause a heap buffer overflow. This overflow can potentially allow the attacker to manipulate the execution flow and execute arbitrary code on the system running the Squid server, resulting in a system compromise.
Conceptual Example Code
Here is a conceptual example of a URN request that could potentially exploit this vulnerability:
GET urn:a:b:c:d:e:f:g:h:i:j:k:l:m:n:o:p:q:r:s:t:u:v:w:x:y:z HTTP/1.1
Host: vulnerable-squid-server.comIn this example, the URN string is intentionally long and complex to trigger the heap buffer overflow. The URN string may be filled with malicious payloads designed to manipulate the execution flow on the server.
Mitigation
To mitigate this vulnerability, users are strongly advised to update to Squid version 6.4 or later where this vulnerability has been fixed. If upgrading is not immediately feasible, temporarily disabling URN access permissions can serve as a workaround. For additional security, deploying a web application firewall (WAF) or intrusion detection system (IDS) can help in detecting and blocking attempts to exploit this vulnerability.